Google Blog Search - Find blogs on your favorite topics

Blog Search - Search for a blog, add your own blog, or grab an RSS feed on the blog topic of your choice. From Jayde Online

Blog Search Engine - also has a directory structure

eatonweb portal - Started in early 1999 when there were less than 50 known weblogs. Over 10000 listed

Technorati - new keyword search feature provides you with the most up-to-date search of all of the weblogs that Technorati tracks - over 1,616,471 at last count