its never the number of blog directories that counts but the blog directories also need to bring some real traffic OR at least have a high PR as backlink benefit - best both here a smaller list of a few dozen i use myself http://www.kriyayoga.com/how_to/how_to_rss.html its a combination list of rss feeds and blog directories. there are HUNDREDS of directories - most of them listed here in DP forum in earlier posts - but most of them only list links and bring no traffic at all ultimately its only about generic traffic !
Look at this list made by Chetan http://forums.digitalpoint.com/showthread.php?t=423444 There are tons of them around as Hans said. Go to the directories forum regularly. Google for the term. You will get a fair amount of directories for submission.