Battlefleet Gothic

The Eldar Webway
Contains Eldar ship names, unique weapons/equipment, and an appendix. Not yet updated regularly, but is supposed to eventually include an Eldar fiction section.
http://www.geocities.com/Area51/Quadrant/2942/index.html

Port Maw
Extra rules, new ships; some Chapter Approved, along with scenarios, general articles on BFG, and fiction.
http://www.portmaw.com/e107_plugins/content/content.php?content.163