There is quite a bit of documentation included with the package, including man pages, and lots of .txt files with hints and useful info. This is also available from the web page. A list of Samba documentation in languages other than English is available on the web page. There is a mailing list for discussion of Samba. There is also an announcement mailing list where new versions are announced.
All announcements also go to the samba list.
You might also like to look at the usenet news group comp.protocols.smb as it often contains lots of useful info and is frequented by lots of Samba users. The newsgroup was initially setup by people on the Samba mailing list. The samba list is gatewayed to this newsgroup. A Samba WWW site has been setup with lots of useful info.