The good guys.
An American company originally called Helix Code, founded by MiguelDeIcaza (the original architect/author of most of GNOME) and Nat Friedman.
The name is a play on "Simian", and they have a strong monkey theme in their branding.
Responsible for a commercial version of GNOME, which is still released freely as XimianDesktop, and a groupware client for GNOME called Evolution. Ximian are also working on Mono.
They were purchased by Novell in August 2003. Rumour has it that it was so Novell could have a decent Groupwise client for Linux, and indeed the GroupWise connector for Ximian is already in heavy development.