Friends Reunited is one of the best known and most visited UK sites. It's free to register your details and once you join you can track down old friends and read a summary of their life after they left school.

There's also an opportunity to add all your workplace history - so old friends can get in touch with each other, communicate with old school and work friends, arrange re-union meetings, even get re-united with old girlfriends and boyfriends.

You never know what might happen when you get reunited with old friends and re-kindle the friendship. People have even been known to marry or track down someone who they though had gone missing many years ago.