Links
P38forum.com American forum where all the knowledge about the P38 is present. A lot of authors of famous P.38 books are active members and are really helpfull in answering your questions.
Very good site about the P38, owned by a Dutch guy. Every subject is addressed and a lot of examples are shown. Definately a site to recommend!
http://lmd-militaria.com Collection of Leon Despain, a very large collection of rare and interesting items.
http://www.p38guns.com Collection of Mark Castel, a renowned American P.38 collector
http://www.mp40.nl Very interesting website about the MP40