Yesterday I posted a screencast about how to embed a MeeboMe widget right on the desktop using ActiveDesktop. While surfing around to see who else had made use of this, I found a link to a Flickr page from late 2005 where someone was using ActiveDesktop to show their Meebo account, and in the comments was a suggestion for a Mac application called WebDesktop that does more or less the same thing on OS X. It's not quite as good, IMHO, in that upon minimizing your active windows you have to click one more time to make the webdesktop become operational, but still, you don't have to have your browser running, and this could easily be made to run upon startup (though of course the Mac won't be starting up nearly as often ;-). Just something else to experiment with.
Here's your screencast (aggregators and mail subscribers will have to click through to view):