Even though blogs can be completely free-form, many blogs have a focus. For example, if a blogger is interested in technology, the blogger might go to the Consumer Electronics Show and post entries of the things he/she sees there. If a blogger is interested in a certain disease, he/she might post every news article and every piece of research he/she finds on the disease. If a blogger is interested in economic issues, he/she might post links to articles that discuss the economy and then offer commentary on them.
There are people who use their blogs simply as a scrapbook -- a form of online memory. Whenever the author finds a link or a snippet of information that he/she wants to remember, it gets posted in the blog. Even if no one else ever looks at it, it is still useful to the author because the blog is a searchable electronic medium that the author can access with a Web browser anywhere in the world.
In other words, a blog can be anything the author wants it to be. The thing that all blogs have in common is the reverse-chronological ordering of entries. From How Stuff Works (Blogs)
The "Create Post" page offers a WYSIWYG for easier posting and a
"Preview" option so that you can see on the screen what your post will actually look like.
If you're a horrible speller (like me) don't forget to use the handy Spell Check wizard!
What ever you want to blog about...let's go!