There was a thread on interesting websites, but can I find it, no!
Anyway www.friendsreunited.co.uk is a website where you register to meet up with your lovely old school chums via email. A word of warning though, you can't just go for a nose around, you have to register first(free). If you want to have everyone's email addresses you need to pay £5 for a years subscription.
There are about 10 listed on my school's site for my leaving year 1983, my friend F and I are having a whale of a time recalling everyone's nicknames etc!