I try to be as complete as possible whenever I research a sample source artist/band (that is why James Brown and Barry White are going to take me some time). This of course implies a lot of Googlistics, as you might expect. But there are also a couple of sites that make my life a bit easier.
Information on artists
Good sources of information (biography, discography) are allmusic.com, ArtistDirect UBL and MSN Entertainment. Yahoo! Launch is less complete, Minnie Riperton is apparently not even an artist worthy of a biography. MusicMatch has great info too, but only through their MusicMatch Jukebox (and not copy/pastable 
)
Information on sample sources
The best source I have found up till now is the-breaks.com. A lot of its content is more or less copied on www.vinyl.com. For the isolated artist (sampling or sampled) you can be so lucky to find a list as complete as Gangstarr Samples. The rest is inventive Googling. A search for “Barry White Sample” gives back 183 hits. “Sample of James Brown“: 45 hits. You get the idea…
I’ve listed some of my resources on Xampled Links.
what is the sample contained in Eric B & Rakim’s “Microphone Fiend” I know it’s Bootsy Collins But I don’t know the song title.
Great Links,great Blog, Great Work
Two more Links: Prodigy Samples and Secondhandsongs
Here some of my found Samples.
Cheers
Another great resource is the listing of all copyrighted composers themselves (plus it includes the stage name, if applicable): http://www.ascap.com/ace/search.cfm?mode=search
It’s quite interesting of all the covers on certain songs…