Apple released a low-end headless Mac, the Mac Mini. The newest Mac offers the following features:
1.25GHz G4 or 1.4GHz G4 for $US499 (listed at $AU799) or $US599 (listed at $AU949)
6.5 inches wide and 2 inches tall
2.9 pounds
Up to 1GB of Memory supported (comes with 256MB)
ATI Radeon 9200
iLife '05
Keyboard, Mouse, and Monitor sold seperately
It can be found on the apple site here: http://www.apple.com/macmini/
They have also released the ipod shuffle, a flash based mp3 player. Found here: http://www.apple.com/ipodshuffle/
The Mac mini looks pretty sexy, and I know of a friend who really wants one. I might look at getting on too. Although it isn't any faster than my ibook. Still it is a very small sexy little computer.
These things will also run linux and other unix operating systems. Quite a few people are looking to turn these things into mini servers.