I have one! It's not a very good example of regular posting and has a very small readership, if any. But, I post it because it's interesting to me. I try to tie in my blog with my website and to showcase whatever project I'm working on at the moment. Ramblings about my cat often end up appearing as well.
http://newgraymare.blogspot.com/I totally agree about the theme thing! It's very important to have a design/theme that fits your personality and whatever it si you're blogging about. I tried to find the closest theme to my websites design. Whenever I feel that my website design is 'finished,' I'll sit down and do the css to make the blog match exactly.
Good luck on your blog! Be sure to give us a link when you get it made =)