Office Content Hosted
I stumbled across this site only4gurus that hosts tons of Microsoft content ranging from samples to slides and whitepapers. I was surprised when I found content from both myself and Chris Kunicki up there... hmmmm... always was worried people actually read that *stuff* :/
Anyway, they have a whole section on Office both 2003 and older. The materials range from new concepts to older issues and it can be quite useful.