The Utlra 60 is a good machine to get. It's cheaper than the Blade 100 or Blade 150 and typically has better performance.
I consider a configuration with two 450MHz CPUs and either 2MB or 4MB of cache RAM. 20 or 30GM of HDD space or more.
At least 1GB of RAM.
Typically prices range from 300 to 500 USD..
Check out eBay.. sometimes you can find good prices on there.
**broken link removed**
Hope this helps.