Ximian GNOME makes for a great Linux desktop. I just did a fresh install of it on my Redhat 7.1 box and it went smooth as silk.
Their site boasts "The Open Source Desktop Leader" and I'd have to agree with them. The latest addition to their suite of products is Ximian Evolution (screenshot), a very nice groupware product (kind of like Outlook 'Lite'). The Ximian desktop is very friendly, offering a number of different looks ranging from Mac-ish to Windows-ish. Nautilus (screenshot) is the file manager and is very clean and user-friendly as well.
Ximian has put quite a bit of work into Ximian GNOME-- I think it raises the bar for other Linux desktop products, and certainly puts Linux one step closer to becoming a true consumer-grade O/S.