I just started seriously using Microsoft Outlook 2007 mostly for the calendar feature. I knew that it could be synced with my 8900, but I had no idea how. After searching the BB Suport Forums, I found the solution which is quite simple.
I just found an even better tutorial on CrackBerry.com in the 101 Lecture Series section:
Check it out. Its great to have a real backup of all contacts, calendar entries, messages and even memos. The 2 way sync makes it nice to make sure you're always up to date.