Two other Fallout games were published by Interplay, but Black Isle Studios had a minimal role in their development and neither spin-off was a CRPG. Fallout Tactics was developed by Microforte, with the support of 14Degrees East, Interplay's tactical games division. Fallout: Brotherhood of Steel, was developed by an in-house division of Interplay and was part of their consolidation around console development.
Bethesda licensed the Fallout setting from Interplay in 2004, although the game remained in pre-production until after the release of TES IV: Oblivion. Recently Interplay sold all rights to Bethesda, and is now licensing the setting from them in the development of a Fallout MMORPG.
Eventually we would like to include an overview of all four games in this thread, but in the meantime here are some general links:
Wikipedia's article on the http://www.gamesas.com/redirect.php?site=http://en.wikipedia.org/wiki/Fallout_series#Fallout
http://www.gamesas.com/redirect.php?site=http://www.falloutvault.com/index.php?title=Main_Page, a fan-made Fallout Wiki
Per Jorner's comprehensive walkthroughs for http://www.gamesas.com/redirect.php?site=http://user.tninet.se/~jyg699a/fallout.html and http://www.gamesas.com/redirect.php?site=http://user.tninet.se/~jyg699a/fallout2.html
The Official websites for http://www.gamesas.com/redirect.php?site=http://www.nma-fallout.com/fallout1/official_site/, http://www.gamesas.com/redirect.php?site=http://www.nma-fallout.com/fallout2/official_site/, http://www.gamesas.com/redirect.php?site=http://www.nma-fallout.com/fallout_tactics/official_site/, and http://www.gamesas.com/redirect.php?site=http://www.duckandcover.cx/official/fobos/ as well as the original http://www.gamesas.com/redirect.php?site=http://www.duckandcover.cx/official/gurps/ and the http://www.gamesas.com/redirect.php?site=http://www.duckandcover.cx/official/bible/. These have been archived on http://www.gamesas.com/redirect.php?site=http://www.nma-fallout.com/ and http://www.gamesas.com/redirect.php?site=http://www.duckandcover.cx/.
I would also like to thank Briosafreak and MrSmileyFaceDude for their assistance with this overview.