Our agents are everywhere...
Wow, that sounds like an awful lot of work. I'd probably just pick one such site and ignore the others, but that's on account of me being very, very lazy.
"Are you going, let your friends know on..." and when you hover over it shows a div containing a nice vertical list of all the sites?
Richard managed the choices, cleanly, on Sparkletack: example above the comments here: http://calyxdesign.com/2008/05/15/all-roads-lead-to-blackletter/
Also, Vox does the same choices vertically with little boxes when you complete a post. You know the guy who owns SixApart?
A couple of options worth considering.