Mp3 Search - Calls your choice of 1 of 30 MP3 search engines. Plus good background info on the MP3 format. SavvySearch MP3 - A meta searcher which searches 8 popular MP3 search engines. Net - multimedia search engine for audio, video and images. Search MPThree - Not a search engine itself.
Form can call multiple search engines simultaneously.
SearchFast for MP3s - Search from a list of popular MP3 searches. Also includes a browsable archive and links to tools, skins, hardware and software. You can optionally give it your email address and it will mail you the results when its done. It checks all results to see whether the server actually up at the time of the query. You can also find thousands of Lyrics and CD Covers.