Unfortunately most blogs I read so far were just boring; either as up-to-date like yesterday's newspaper or so obviously written just for marketing purposes, that they were not worth the time reading them.

Anyway, this also means that an informative, carefully written blog has good chances to get popular :-)

Regarding where to start a blog... call me paranoid, but I tend to have my blog hosted on my server. Consider that the blog site you write in goes offline, then all your work is lost.