I'm only going to say this once - if you use Microsoft Entourage make sure to properly back up the ~/Documents/Microsoft User Data directory frequently!!! Having just gone through a horrid experience with this Microsoft product, I can't stress this point enough.
I don't use Entourage by choice. Enough said. This week I learned a valuable lesson about backing up this huge directory (>250mb). If Entourage has a problem using it the only way to easily get back the data is from a backup. BTW, the Entourage Help Page was helpful with this and I've found many other little tidbits of good info there or at the Entourage Help Blog.