Housing for spiders can vary from a very simple enclosure with a slab of bark and a water dish, to a naturalistic vivarium furnished with wood and live plants. Hobbyists use a wide range of containers to keep spiders that vary from tupperware and deli containers to custom built acrylic and glass enclosures designed especially for the type of species you are keeping.  Aside from basic environmental needs, there are few limitations as to how or what you will keep your spider in.  The biggest limitation is probably that of your budget .  Luckily, great tarantula enclosures, especially for small spiderlings can be very inexpensive or even free in the form of discarded food and drink containers and supermarkets or craft stores can offer you an endless variety of excellent housing options for less than 10 dollars.  If you are demanding a more upscale look for housing your collection various containers which offer superior clarity and security are available in the form of plastic vials and acrylic cubes.  There are also a few companies which are currently offering custom designed enclosures which not only look really amazing but also offer a healthy, well ventilated environment.  

No matter what type of enclosure you decide upon...just be sure to provide a few basic needs, the rest is up to you. First, you must familiarize yourself with the most basic  needs of the species you intend to keep.  A responsible owner should do research before acquiring a tarantula. your spider's requirements ahead of time. Don't try to mimic a spider's natural environment too closely as it's difficult to accomplish this in a relatively small space.  Although a tarantula species may come from somewhere in the desert it doesn't mean you should keep their enclosures really hot.  In general, external heat is usually a bad idea.  Most spiders do best with being kept in a relatively warm room, I usually don't let my spiders get far above 80F. 

 Many people like to use live plants in enclosures but artificial foliage is just as effective.  Tarantulas will often burrow down into the substrate, uprooting and killing many of the more delicate plants decorating the enclosure. Some of the arboreal species may build elaborate tube webs that can wind upward in the enclosure encompassing and killing most plants if not seriously limiting growing space.  It's also difficult to maintain the proper light requirements necessary for most plants as tarantulas generally aren't fans of bright light. Perhaps the only species of plant I could recommend to co-habitate with tarantulas is pothos which is a common house plant requiring low light levels. It's best not to use any fertilizers in your spider's cages, this is especially important when choosing a substrate.

Substrate 

For my arboreal tarantulas substrate, I like to use a mix of ground peat moss and coconut coir commonly sold in compressed bricks.  The acidic qualities of the peat keep fungus from developing and the strands in the ground coconut husk help to keep the soil from collapsing for tunneling spiders and air out the denser peat material. I also like to add a bit of sand to the substrate which is thoroughly mixed through in order to provide some drainage and keeps the substrate from becoming too compacted. The combination is a fluffy mix that has good anti-fungal properties and retains lots of moisture. Be sure to provide a generous amount of substrate which serves as both a burrowing medium and building material.  Many juvenile tarantulas like to burrow down into the substrate and build a tubeweb upwards which they line with the substrate.  In some of my larger containers and enclosures, I like to include a drainage layer which allows for the substrate to stay adequately moist but never saturated which promotes bacterial/fungal growth and substrate dwellings pests such as phorid flies and fungus gnats.  This layer can range from simply some gravel set down before the actual substrate to a more elaborate multi-level system that I like to use in some of my larger containers. 

When the substrate layer has a good amount of drainage it keep a healthier environment for the humidity loving species being kept.  I like to keep a drainage layer that consists of a bottom layer of expanded clay pellets, fiberglass mesh, long-fiber sphagnum moss and ultimately a generous layer of the top substrate.  Although many arboreal species are prone to burrow down they will usually stop at the fiberglass mesh level.  Below is a breakdown of the drainage levels.

Drainage layers in a large custom arboreal enclosure.

The final product.  The top level of substrate consists of a mix of peat moss, coconut fiber coir, and coarse sand (excuse the condensation in this picture).  It's important to give a generous amount of top substrate in order to keep the tarantula from burrowing too deep down into the substrate.  Even though they are arboreal they like to retreat a few inches into the substrate and even incorporate part of the substrate  into the tube web.

Cubes
For Juveniles I like to use cubes of varying sizes which are purchased  at Micheal's or similar craft stores.  I use cubes as small as 1 or two inches square up to about 4 inches in width.  I prefer the cubes to the round pillbottle type vials used by many hobbyists simply because the shape keeps them from easily tipping over.  I like to keep multiple cubes in a larger plastic enclosure and the square shape lends support to the container next to it. The larger cubes are easily displayed on a shelf and make a great enclosure for juveniles up to sub adult animals.  

 More Containers

1 Gallon clear plastic Jars make excellent enclosures for rearing most arboreal spiders, the ones I use measure approximately 10"high and 6" accross and are manufactured for the food industry.  These jars are best for subadult and adult arboreal tarantulas. 
They also work well for keeping some of the more terrestrial species in that they afford a deep substrate layer which allows for proper burrow construction.  Once again it's important to ventilate accordingly as well as provide drainage holes to prevent water from pooling in the deep substrate layer.

A slab of bark cab be placed in the jar leaning to one side in order to provide shelter and foundation for webbing.  With some arboreal tarantulas like Avicularia you don't need to get too fancy with cage decor or even hiding shelters as they will completely web up their enclosures once acclimated. Some support structures such as branches are usually incorporated into their 3 dimensional webbing structures but they aren't really necessary.  For some of the more "nervous" arboreal tarantulas like Psalmopeous and Poecilotheria a retreat in the form of a piece of bark or some wood is much appreciated.  I like to use slabs or cork or cork bark tubes in my enclosures which are secured to one side with the help of a hot glue gun.  I like to secure all wood because even the slightest shift could severely injure a tarantula.

Adults of most arboreal species including Avicularia, Psalmopeous, and some Poecilotheria can easily be maintained in these jars but for breeding and housing some of the larger Poecilotheria sp. I recommend something more spacious and accessible. It's best to have plenty of room to maneuver when it comes to fast or potentially dangerous arboreals.  I think that for breeding purposes it's best to house females in larger enclosures.  The larger the enclosure the more room the male will have to maneuver himself into position for a successful insertion.  Having the extra legroom will also increase the chances of a successful retreat.  As great as the jars are, I found tanks to better suit adult females you intend to breed.
 

Ventilation 

It's critical to create plenty of  air holes for proper ventilation to prevent a stagnant and potentially dangerous environment.  Tarantulas respire very little but they require a well ventilated environment or will quickly die. Too many air holes can also work against you in that the containers will quickly dry out.  Nothing kills a sling quicker than a dried out container.  Not enough holes and you will have a very moist environment and you will see mold and fungus easily developing on the slightest bit of organic debris.  There's a careful balance that needs to be achieved by creating the right number of holes.

Be careful with smaller spiderlings and air holes, they can be very adept at escaping through unbelievably small ones. I like to use a soldering iron or occasionally a fine bit  on a drill to create small ventilation holes.  If the hole comes out too big or I'm doubtful as to its ability to hold a sling I will just close them back up with a little dab of glue from a hot glue gun.  It's best to place holes both on top and on the bottom of the containers in order to promote good airflow.