For mods check this list:
GWX 3 Wilhemshafen,St Naz,Schluese and xtra ships V5
GWX - 20km Atmosphere (Unofficial Mod)
DD_OH_V3.09_20091209162038
Enhanced Funnel Smoke and Thomsens Ships V4.1
LifeBoats&Debris_v4
GWX3.0 Additional_Ammo
GWX3.0 All_Weather_Guns
Historic Turm Pack v1
GWX - Enhanced Damage Effects
Torpedo damage Final ver2.0
OLC 'Gold' MkII ~ Flat Sun Fix
Hitman U-505 Compass Graphics v1.0
Radio Deutschland
Radio England
Radio France
Radio USA
There is also a new mod by Flakmonkey which will let you "walk" through some additional compartments.
http://www.subsim.com/radioroom/showthread.php?t=162631
Check out the SHIII mods section and you'll find plenty of other good stuff.