Google Voice

I've been using Google Voice for a few weeks now and I am really impressed.

From my perspective the most useful features are:

1. Ringing multiple phones at once
2. SMS transcriptions of voice messages
3. Online access to calls, transcriptions of calls, SMS history
   
4. Routing of calls based on caller, time of day.
   
5. Call Screening / Listening in on calls
6. Cheap International Calls

Quite impressive -- Google continues to impress me.