I came across this site today. Had found it previously but had to search again so I could bookmark it.
http://www.svgames.com
You can download old edition books for a few dollars each. The Rules are old but more importantly lots of background info and ideas. You could download some of the books for nothing though at the Wizards site.
Edit: just checked ebay. until a few days ago I had never been there (except maybe once for a few minutes a few years ago). I am surprised a search of "D&D 3.5" only had 2 pages. You say you picked up Unearthed Arcana. I know it has optional rules. I am interested in the rules for sanity.
[ August 02, 2004, 13:34: Message edited by: Randallw ]