I recently came across a blog about volcanic eruptions. Eruptions is written by a geologist and I highly recommend it to anyone interested in volcanoes. There are a couple of really interesting posts about Vesuvius:
Vesuvius also features in the discussion of other volcanoes on this site. There is also an interesting comparison between the eruption of Vesuvius in AD 79 and that of Mount St Helens in 1980 on a related ScienceBlogs site: A tale of two volcanoes. And you can find a brief history of the eruptions of Vesuvius here.