Just found a brilliant website for us Brits - I think you have an equivalent in the US though.
. http://www.friendsreunited.com
Once you register, which is free and very easy, you enter the name of your old school, primary, secondary or both and it gives you details of kids you went to school with, what they did after they left, what job they are doing now, whether they got married and had kids, etc. For a fee of £5 you can then choose to contact any of them, although some manage to sneak their email address on without being noticed by the moderator it seems.
Bringing back fantastic memories for me, so many familiar names and faces, and who would have thought the class swot would have ended up on a building site and the girl who never brushed her hair and wore naff clothes would end up being a top graphic designer with her own company. Amazing site.