Right now, you can check out what your Xbox Live friends are up to from your phone, but you can't actually manage your friends list from any of the mobile Live apps (and Xbox Live Anywhere has gone MIA again). But the developer of one of the better ones, 1337pwn, says that Microsoft has made a change to the site that makes it possible to add friends remotely, and he thinks "that we can get it working," though he's not making any promises yet. Now if Microsoft would just lift that damn 100 friends limit so you actually could add more friends. [MTV Multiplayer]
This is cool, and am looking forward to using it. I do not like having a crap ton of friends though, as you get distracted by people bopping on line all the time during games.
Keep the list simple and small. That being said, if you want to add me, zenpoet is the name for live as well. As long as you enjoy gaming and are not a screaming 14 year old boy, you could probably make the cut.