There are a variety of factors to consider when selecting a web host for your blog, but above all is reliability.  No amount of cool features can compensate for downtime.  Because of this, I typically recommend using one of the larger hosting companies, as they have the resources and capabilities to maintain the proper equipment and facilities.  Options include companies like GoDaddy, BlueHost, and HostGator.  I personally have had a good experience with HostGator, and they have a variety of plans available, but any large hosting company is a better bet than small fly-by-night company.