So I finally found the right place to look up journal impact factors. The ISI Web of Knowledge Journal Citation Reports service. However you need to subscribe to the service, and most universities do, so I have access through University of Hawaii. I was particularly interested to discover that they have an API for their service, and that someone has already written a ruby client for it:
I also found some interesting discussions by people who would like to sort PubMed records by impact factor:
a non-subscription based site for access to slightly older impact factors:
and a series of articles on impact factors, cite-ranks and other fun stuff:
It seems that impact factor ratings are not without controversy. Anyhow, I haven't really digested all this, and I should probably stop procrastinating and get on with my literature review, but it makes me think that I could modify my Google Scholar system to lookup citation counts both on google scholar and also through ISI and then compare them to see how different they were, which might be realllllly interesting, and possibly generate enough data for a conference paper ...