There are two that I know of:
# Develop for Windows, which does not seem to support ASP.Net very well
and
MonoDevelop for Linux, Windows, and soon Mac OS. Based on #Develop, with changes for Mono / Gtk #, and has better ASP.Net support from 2.0, which is currently in beta .
, CLR/DLR, Boo, IronPython IronRuby.