Icesphere uses GTK# to manage its user interface. Microsoft Windows and Apple Macintosh OSX users that aren't familiar with GTK may find this helpful. Linux users probably already have GTK installed and just need GTK# and dependencies.
Windows user can now use use the Icesphere installer which includes GTK#, found on the Icesphere Download page.
Tips for Linux users:
Debian: apt-get install gnome-desktop-sharp2
Gentoo: emerge dev-dotnet/gtk-sharp dev-dotnet/glade-sharp
For all others: You can select your the appropriate download at the Mono Download page, which has the GTK# run-time downloads and installer.
Please comment with any further links that you found helpful.