Alltop [0] is great. BlogRank [1] is good too. Look at the sources that bigger news sites get their leads from (the via link at the bottom of articles).

Spend more time than you think necessary writing really great emails for the editors of the smaller blogs. Include a press kit with the stuff they'd need to write a nice looking post: generally a couple photos/large logo and a bullet point description of your pitch and company story.

[0] http://alltop.com/

[1] http://www.blogmetrics.org/