I think there are still some LLL.in available... and a LLL has usually more value than a NNN. Correct me if i am wrong.
Information from 3character.com:
3-Letter .com - $3350 (+ $100 since February 1, 2007 report)
3-Letter .net - $710 (+ $10 since February 1, 2007 report)
3-Letter .org - $250 (+ $10 since February 1, 2007 report)
3-Letter .info - $135 (+ $5 since February 1, 2007 report)
3-Letter .biz - $80 (+ $10 since February 1, 2007 report)
3-Letter .us - $110
3-Letter .mobi - $140 (+ 10 since February 1, 2007 report)
3-Number .com - $5400 (+ 400 since February 1, 2007 report)
3-Number .net - $825 (+ $25 since February 1, 2007 report)
3-Number .org - $325 (+ $25 since February 1, 2007 report)
3-Number .info - $185 (+ $10 since February 1, 2007 report)
3-Number .biz - $95 (+ $5 since February 1, 2007 report)
3-Number .us - $165 (+ $20 since February 1, 2007 report) - (Note: These are the rarest of the NNN Domains, as the registry holds a high percentage of NNN.us names)
3-Number .mobi - $610 (- $140 since February 1, 2007 report)
Usually NNN have a greater value then LLL but this must be considered on an individual domain basis.