Quick post for a Saturday morning ... I just read about BlinkX's API offering, which the call "Red Label". They provide both a hosted solution, or an XML API solution, allowing you to freely (up to about 10,000 / queries per day ... if you have more, then you'll need to negotiate with BlinkX). Currently, BlinkX searches over 26 million videos and they also index selected audio sites as well.
Read more about the BlinkX Red Label program at: http://www.blinkx.com/redlabel/introduction .