MOTM

http://www.benchmarkmedia.com/micpre/mp3/default.asp

This is the Benchmark Media MP-3 mic preamp module mounted on an XLR jack.  
Benchmark stuff is REALLY  nice and sounds great.  Will work on a bipolar 
15Vdc supply.  Just add a panel and you're all set!

For the really tweaky people out there step up to the MP-4:

http://www.benchmarkmedia.com/micpre/mp4/default.asp

Ivan