Technorati

Using advanced search will vary your results byoffering a choice to narrow or broaden your results by posts or by subject relevancy within the blogs. With Blog Directory Search there are three search settings to choose from : relevance results in 431 blogs, authority gives 454 blogs, and freshness results in 452. If I use tag search my results come out to be zilch.
Keyword search results let you also choose the level of authority you want to access. For the highest authority level library 2.0 found 1.030 results and the lowest (any) authority level found 7,503 pertaining to library 2.0. Tags with highest authority found 107 results, and lowest found 2,056.
Technorati lets you manipulate your search results and this I find to be very helpful. Sometimes you want to find blogs on a topic that will have relevance to them. Listing authority levels helps your decision-making.