Fursuit.com (previously fursuit.org) Mail list and FAQ. The Original Fursuit Information Source.

Let's face it… Not everyone wants to buy a commercially-available pattern for their fursuits or other items. Sometimes they'll just wing it in the hope that it'll turn out perfectly, and it does at times. Jersey work gloves and garden gloves can be taken apart quite easily and used as a pattern. You may have to measure your own fingers to get the fit right.

Kerry has a good page telling how to do a catsuit, and goes on to tell how to do other things - http://www.maskon.com/kerry/kerry6.htm

A number of free custom-fit catsuit patterns, created by Tim Baverstock. Attached gloves and socks optional - http://www.stretchy.org/catsuit/

Damian K's How To Make a Skinsuit site - http://www.weaponofcreation.com/files/ies/htskin.htm