I'm presuming you are talking about readers of audio books...
I don't know of a single site that does this, but for US narrators --
http://www.recordedbooks.com
-- seems quite comprehensive, and for UK narrators, try the audio books section of waterstones/amazon and type in the FULL NAME of the narrator. You'll get a very full list, but I don't think it is absolutely complete
http://www.amazon.co.uk/exec/obidos/tg/browse/-/51
/ref=br_bc_h_2_32/202-2766898-0882247
-- other reference points might be: --
http://www.powells.com
-- (allegedly the world's largest stock of rare and out of print books (including audio)