I love this app on my windows box. imeem. If you are into social networking software, this is one of the best. They do some absolutly amazing things with GDI+ with SWF on Win32.

IMEEM LOGO

They just released their new mac client. It runs on top of Mono and binds to cocoa using a new interface they designed called Dumbarton (released under LGPL). Good work guys!

Now, since you got Todd Berman from (but not limited to) MonoDevelop over there now, I expect a native GTK# interface soon too… :-)