Django, Rails, and PHP
Sam Newman has posted a useful high-level comparison of Django and Rails on his site. In it, I think he hits on one little-discussed reason why these two projects are grabbing so much mindshare right now:
[Rails and Django] … historically would have ended up being written in Perl or PHP - but ended up being written in Ruby and Python respectively.
When I heard DHH speak at OSCON, he mentioned switching to Ruby after giving up on trying to make PHP do the kind of stuff he wanted to do. Back in July I asked Simon Willison (of the Django team) about PHP; he said that both he and Adrian Holovaty had worked in PHP for years, but it was Python that “gave us the flexibility we needed to pull everything off.”