Two years ago I had an idea of a web application that reminds you to keep up the contact with friends on a periodic basis. Now I've put together a new web application that does exactly that called RememberYourFriends.com and is fully working but might get a few more features added later.
RememberYourFriends allows you to tell which friends you want to be reminded about and how often. If it's a really close friend (eg. your own parent and you just moved away from home a week ago) you might set the reminders to be sent every week. If it's a old class mate who you just want to make sure you don't loose contact with completely you set it to remind you every 6 months instead.
The reminders are sent to you via email which makes it very easy for you to go from reading the reminder email to composing a new email to this friend. If you at the current time don't have time to send an email to this old friend, just click one of the "snooze links" and the reminder will be sent again in a day or a week depending on your choice.
One very different thing about this system is that you really don't need to remember no username or password even if you can log in. The first time you sign up and set up the first reminders your passkey is automatically remembered in a cookie. The next time you snooze a reminder or follow any of the links in the next reminder sent to you you'll be automatically logged in again. The only time you might need your passkey is when you move from one computer to the next where you don't have your previously set cookie and you might not immediately have a previously sent email near by. For most users however, you'll have a secure account but you won't have to remember anything.
This project started because I personally wanted something like this. I move from PDA/mobile every so often that I often loose any reminders I might have in my PIM at the time. This service is here to stay. Another reason for doing it is that I wanted to experiment with some new concepts for web application design such as the automatic login processes.
Please give it a try. I'm sure you also have past friends who you feel that you want to maintain the contact with but isn't keeping in touch with enough. It's free, not evil and not connected to any greedy company. Enjoy and please post all feedback back to me.