Open Office 3 is going to fully support the Mac, so no need to pay for Microsoft Office any more!
(The link's just to a brochure - OO3 isn't out for a few months yet.)
Perian is an add-in to Quicktime which will play .mkv files and is WAY better than VLC if you watch anything with soft subtitles.
Flip4Mac is another add-in for Quicktime which plays Windows Media files.
I believe the latest Quicktime does let you view in full screen mode without having to shell out for Quicktime Pro.