To research the federal recognition (aka federal acknowledgment) process for American Indian tribes at the National Indian Law Library, start at this web page: http://www.narf.org/nill/resources/recog.htm
A list of tribes recognized as of 2007 is linked, in addition to Bureau of Indian Affairs Acknowledgment Database showing the status of tribes. (last updated August, 2004)
The library has numerous materials on federal recognition. Go to the library's catalog (http://nillcat.narf.org) and type "federal recognition" in the subject field. A new book at the library on this process is Forgotten tribes : unrecognized Indians and the federal acknowledgment process / Mark Edwin Miller. Federal recognition documents for various tribes can be found, and numerous journal articles on the acknowledgment process.
Contact the library for more assistance.