Best overall source for B-29 is in my own opinion the '57 Years ago' site (former 56 years ago) with a chronology from April 1944 to August 1945 and details on most losses:
http://home.att.net/~sallyann6/b29/56years-4404.html
There is also a forum active on the Net:
http://www.armyairforces.com/forum/forumid_130/tt.htm
A Google search with "500th BG" and B-29 as the searched terms will bring you 56 pages, the two above are the first, other will be about precise aircraft of the unit, some will show images, most are useless (same text, preface of a book written by a former 500th BG pilot)