Some of you might not know this site yet:
http://www.ubootwaffe.net/
An excellent source of information about U-boats. Be sure to check the Kriegstagebuch Der U-Bootwaffe, where you can download daily operation reports as pdf files (in German). Want to know where your boat was patrolling on a particular day?
Also of interest are complete crew lists for U-boats in case you want to know who was who on the real U-boat that you are playing in SH3.