If you've not tired of creating profiles and passwords and freeing all kinds of personal information into the internet's ether, then take a look at Dopplr. This is one I really like and might actually commit to updating. Since much of my travel is related to business and because I'm lucky enough to work often with some of my closest friends, this site might just really work out. I tried Trip-It but didn't fall in love so I broke up with it (used The Fade Break-Up Method; it doesn't even know I left). Dopplr seems pretty low maintance and fun. It lets you know who else has coinciding trips to yours (which happens all the time with those of use entrenched in the ABA) and it also lets you know which of your friends/contacts live in a city you are visiting.
I created a blog badge for it - which you will see - or SHOULD see - in the right column (stupid IE won't show it for some reason; troubleshoot that later). One of the very cool and yet kinda creepy things it does is allow you to subcribe to another friend/travellers Doppler calendar and add it to your Outlook (and surely other) calendar. Now I can keep a REAL close eye on that legal technology celeb Tom Mighell. Actually, Tom and I were just chatting about it on Facebook (ahuh, you heard right - I got REALLY bored today) and we were saying that we really like the tool just wish we had more friends/travellers on there. So if you make it there, let us know.