Here are some web sites I have found helpful in my research.
The Doolittle Raiders
http://www.doolittletokyoraiders.com/
This is the official web site of the Doolittle Tokyo Raiders who flew a bombing mission against Japan in April 1945. The raid consisted of 16 B-25 bombers launched from the deck of the aircraft carrier USS Hornet.
The Irish Lassie — Main Page
http://mypages.cityhighflash.com/irishlassie.htm
The Irish Lassie was a B-29 that received severe damage in a raid over Tokyo and somehow made it back to Saipan only to crash on landing. The site is maintained by the son of the Irish Lassie's tail gunner.
B-29 Superfortress Then and Now… (AKA: Sallyann's Boys)
http://b-29.org/
Maintained by Sallyann Wagoner, this site is an excellent resource for B-29 information and stories.
Twentieth Air Force Association
http://www.20thaf.org/
Features a history of the 20th Air Force, an archive or newsletters, group information, etc.
The War
http://www.pbs.org/thewar/
The companion web site to The War, the PBS documentary on World War II produced and directed by Ken Burns and Lynn Novick.
Wikpedia, the Free Encyclopedia
http://en.wikipedia.org
IMPORTANT NOTE: Most educators and professionals do not consider it appropriate to use tertiary sources such as encyclopedias as a sole source for any information — citing an encyclopedia as an important reference in footnotes or bibliographies may result in censure or a failing grade. Wikipedia articles should be used for background information, as a reference for correct terminology and search terms, and as a starting point for further research.
As with any community-built reference, there is a possibility for error in Wikipedia's content — please check your facts against multiple sources and read our disclaimers for more information.
— from Wikipedia's article citation page.
Before you think bad of me for using Wikipedia keep in mind that an encyclopedia is a great way to quickly check basic facts. There have also been many times I found links to other excellent sites from Wikipedia that a search engine never turned up for me, or that I never thought to search for. Wikipedia also tries to use media that is not protected by copyright or have been released for public use under a Creative Commons or similar license making it easy for me to find maps and other images to use on my site without fear of copyright infringement. Basically, Wikipedia has been a great launching point for research.
WWII B-29 Footage
http://atheyfamily.org/B29/index.htm
This site is maintained by Christopher C. Athey as part of a heritage/genealogy site for his family. It contains pictures and film clips of B-29s from the National Archives.