Ian Bicking (a python developer I have a great deal of respect for) has a good comparison of Python and Ruby, focusing on the things that are unique to dynamic languages.
link
There’s a relatively in-depth comparison of the Django framework to Rails over at Sam Newman’s site. It appears to be a relatively fair comparison.
It’s interesting that both frameworks were extracted from large development projects in roughly the same time period, although Rails has been publicly available for longer, and has more mindshare at the moment.
I’m happy with Rails, but I wonder whether I would have bothered with it if Django had been available when I started looking at Rails.