There are many types of blogs out there, what it really depends on is the imagination of the person writing it, but we will mention the most common ones here:
Egoblogs: This type of blog is used as a way of replacing the traditional, personal diary. Even though publishing on the Internet makes them not so "personal" you can use an alias. There is also the advantage of being able to add images and music to your post.
Topical: This type of blog can be about anything from politics, religion, sport etc. All you have to do is give your personal opinion on whatever topic interests you and you can then debate with the readers about what you have to say!
Dedications: Blogs can be educational and help you learn about many things, such as crafts, painting and sewing. You can find experts in the area or other people wanting to learn and so learn together by interacting and exchanging comments.
Cultural: Normally blogs dealing with culturally related topics such as history, society, family etc.
Artistic: The most common of this type is a literary blog, where you will find poems, stories and any other type of literary expression made by the author. These blogs are looking for opinions and assessments of the pieces published and also to speak about other authors.
Corporative: This type of blog is for companies to offer their services to others. It's similar to a business website but you can be more widespread across other blogs.
Recreational: A big group of blogs are recreational. There are blogs about jokes, graphic humour and games amongst other things.