DIY projects can be a money saver and may end up higher quality than the mass produced items found for high dollar at the pet store. The following links will instruct you step by illustrated step on constructing cages and more for your animal husbandry needs.
The links provided are chosen strictly for the DIY info.
http://www.guineapigcages.com/howto.htm Instructions for the C&C (cubes and Coroplaast) style of Guinea pig cage. Be sure to look through all the pages-different styles, optional accessories, size guide, details of the materials, where to buy, etc.