2. Slacker (a little buggy, but I like the music selection better)
3. Google Voice (even if just for voice mail, far better than visual voice mail)
5. SportsTap (if you are a sports fan)
6. OurGroceries (if you shop for a family, shares 1 shopping list between phones)
7. OIShoppingList if not OurGroceries
8. Google Goggles (not great yet, just cool to play around with)
9. DockRunner (if you don't want to spend $30 on the media dock)
10. CalWidget (puts agenda on homescreen in multiple widget sizes to choose from)
If you use MySpace or BankofAmerica their apps are good.
That is a good start, there are plenty of great games to kill time, but those are just a matter of preference.