I maintain 8 Twitter accounts. Two (1 professional; 1 webcomic/silly) are mine. The other six belong to webcomic characters. Which means that I do talk to myself through Twitter. Sometimes even arguing with myself. And the characters talk to each other. To accomplish this, I use several different Twitter clients including web-based clients. Twitter.com, brizzly.com, Twikini, TwInbox, Echofon, Spreadtweet, Twitterfeed and SMS/TXT in addition to TwitPic, TwitVid and ScreenTweet.
I maintain 3 Facebook entities. One is my personal account, one is a webcomic character (business account), and the last one is my webcomic's fan page.
I roleplay 2 separate accounts on my forums in addition to my own administrator account: 8PackAlex (Alex) and Poke.
I track two Formspring.me accounts. My own and Alex's. I have artist portfolios on DeviantArt and FurAffinity. I maintain two live-feed streaming accounts. One is on Ustream; the other on Livestream.
I write a personal, friend-locked blog on LiveJournal. I also author my dog's POV blog on LiveJournal. In addition, I have a comic-centric blog and a public personal blog on my website. I also maintain Alex's blog from his POV. And the Rarnar Industries blog.
There is one spin-off, real-world/fake-world website hosting the in-world Rarnar Industries. I maintain this site as well. How do I find time? Don't know. But having less than 55 fans seems to be it. I only have about ten really active fans, the rest just read my page and move onto whatever their next activity may be.
If I had a greater degree of interaction, I wouldn't be able to keep up with it. But because my fans are so passive, it makes quite simple for me to publicly crazy. I must move the car now.