Touchdown
My latest favorite app is Touchdown from NitroDesk, Inc. It is a replacement for the Exchange app that comes with the Android, and what a great replacement it is! I *love* this program. Worth every penny of the $20 it costs if you are a business user and use Microsoft Exchange to access Outlook info - email, calendar, contacts, tasks, notes. On my HTC Incredible it works flawlessly and the interface is very clear and easy to use. Definitely a "top 20" app. It's available for free to try for 30 days. I'm very happy with it.
While I'm here, I'll mention that I second the nomination of Documents to Go. Much, much better than Quickoffice. Another great app.
