Unlike a blog search engine, a blog directory is not based on keywords and a simple search. Rather, it is based on the concept of browsing, and categorization. Blogs are placed in a blog directory based on what their main themes are, and may be placed in one or more categories in a directory tree. The user then makes their way through the directory tree, and in each category or sub-category they are able to see a listing of all of the blogs that were placed in that category. Most directories also include a search engine, but this is a secondary feature.
Here are a list of blog directories you might find helpful: