On my other blog, a WordPress one that I have hosted myself, I have added the FireStats plug-in so that I can get some idea how many are paying it a visit. It has definitely been useful. It tells you referrer, operating system and browser information as well as what has been visited. I know that I can look at my server logs to get this information but this is so much easier and it can be extended to non-WordPress PHP-powered pages too.
Hansel and Gretel Breadcrumb is another plug-in that I have spotted but given that the blog is set-up, it didn’t look that useful. If it could be extended to my non-blog pages à la FireStats, that would be a much more useful situation.