First of all, you must have to know that blogcatlog is a bloggers social network and it provides directory, profiles and a list of discussions. You can submit your blogs into blogcatlog by selecting the category and entering the necessary details about your blogs.
How it works?
Blogcatlog is a collection of large number of Blogs and thus it has good reputation in Google search and more.
As far as I've experienced, I had created a Blog for a friend adder software and submitted it to Google but Google doesn't index it for two weeks. Then I submitted it to Blogcatlog and saw the difference. When I searched with URL Blogcatlog entry appeared in the Google just after 2 hours and then on the same day my Blog appeared in google. Actually Blogcatlog provide backlink to your Blog, which makes your Blog more SEO friendly and it provides high priority in search engine ranking to your Blog.
Whenever you post anything in your Blog, Blogcatlog create a page for that entry and show the post title, post URL, small description so you get more traffic and good SEO rating. Even I am getting approximately 50 traffic to my Blog from Blogcatlog till now.