BookGlutton.com — A social website where instead of commenting on articles (like digg.com), you comment on books. You can even do IM with people who are reading the same book as you at the same time.
Pipl.com– Wh0 needs an address and phone book anymore? This is a free service and does better than just about anything at finding evidence of anyone on the internet. Good enough for most applications. On my name, it returns about 80% false matches (same name, different person). But the remaining 20% is probably 70% of all the online accounts and profile pages that exist for me.