making your own aquarium is actually pretty easy especially if it's small (like 6 gal for example). five panes of glass, some silicone sealant and boom shakalaka you're done. Here's where I learnt how to do it...
http://saltaquarium.about.com/cs/aqu...20897diyaq.htm
Unless you're planning on putting something like a mantis shrimp in there I would stick to glass for simplicity sake. If you go acrylic, it's more expensive (but only slightly... gets worse if you make a big tank), and a little trickier. You'd need acrylic solvent (like weld-on #3 which as consistent as water) and then a "just in case sealant" (like weld-on #16 which is goopy).
To get all the stuff just look around at a home depot, glass/plastics supplier, or even an autobody shop.