I recently acquired two guinea pigs (long story), and although they are small now (about the size of a large hamster), they're going to get bigger over the course of the next few months (about the size of a small rabbit), and we'll soon need a larger cage to put them in. The cages which the pet store sells are generally two small for them to really have room to move around in, and the ones which are larger are very expensive, in the $125+ range. When exploring my options, I came across a great site which I wanted to share with you all here. The site is called Cavy Cages, and it explains how to make an easy, fully customizable pet cage for around $30 using those wire grid storage cubes and some plastic sign material. What's great, I think, about making the cages this way is that you can make them larger or smaller based on your size preference and exact space allowance, they can be easily taken apart and stored, they're easy to wash, and if you decide to go a different route later, you can simply turn them back into storage cubes in a snap!

http://www.guineapigcages.com/howto.htm

They sell kits on the site to make the cages, but there's no need to buy them as many stores sell the storage cubes, including Costco, Wal-Mart, Target, K-Mart, Bed Bath and Beyond, office supply stores, etc.