FellowUp is a free service that basically acts as your personal virtual assistant. It's not one of those outsourced personal virtual assistant programs where you pay a low fee for someone to handle your menial tasks, but rather an intelligent webapp that takes data from your various online accounts and helps you keep track of it all. Additionally, FellowUp provides you with several options to interact with your contacts directly from the webapp.
For example, take a look at the image on the left (click it to enlarge). Two of my friends have birthdays today. I can click a button within FellowUp to write on their wall or send a message and FellowUp even provides that message. If I'd prefer to use a different message as a template, I can check a box to use the current message as a template. This is an example for facebook and birthdays, but this sort of simple communication works with all of your linked accounts. You don't have to actually go to the sites individually because you can communicate through all of them from a single location.
As you do more with FellowUp, it'll learn what's important to you and start notifying you of relevant updates in your network. If you meet new people, or have trouble keeping track of the ones already in your network, you can add private notes to remember important bits of information you might need next time you want to interact with a specific person.
Basically, FellowUp is a set of tools to help you maintain meaningful connections with people. It's available for as a webapp and as an app on your iDevice (with an Android version on the way) and you can sign up for free, right now, if you want to check it out.