Yes i have a blog related to SEO and 1 another blog related to Photo and wallpapers.
I have several... I find that Wordpress is simply too easy to use and that comes in handy for someone that is HTML ignorant! Though, for a few of my sites something like Joomla may be more suited, but I've just not gone there...
I have a few niche sites that run on Wordpress, but I wouldn't call those blogs because a blog is something that you update often and niche sites (at least mine) get content like once every 6 months. So I would say that I don't have a blog...but I recently bought a domain and will probably maintain a personal blog on that domain.
I have a lot of blogs include this blogspot blog at my signature.