Hangouts
LiveJournal.com - Great place to blog/journal and also a central fannish location these days. My friends-only journal is located here.
Last.fm - Download a small, simple program that works with your music-playing program and can sync with your mp3 player to track what you listen to and how often and compile nifty little charts to put on your websites and whatnot.
DeviantArt - Great place to post a wide variety of artistic works.
Ravelry - A knit and crochet community
Fandom Wank - Mocking the craziest of the crazy fans for fun and great justice.

Good Reads
Although I do most of my online socialising on LJ these days, there are still a few blogs I swing by with some regularity:
Go Fug Yourself - Making fun of celebrity fashion faux-pas with plenty of snark and the occasional visit from Intern George.
Smart Bitches, Trashy Books - Smart bitches who read romance novels and talk about them with much hilarity.
VlogBrothers - A great video blog by two brothers, one of whom is a successful YA author.