There is really no point to this post except to remind me of all the Python ORMs I promised myself I'd look at over the summer. I want to convert my web application from raw SQL(ite) to some ORM, but there are way too many of them. I could roll dice, but that doesn't seem appropriate somehow... :-D
And then there are these Gadfly and buzhug and SnakeSQL things, not ORMs of course, but interesting anyway...
Update 2010/06/24: Alright, I've looked at a few of these in more detail now. Seems that Autumn has not been updated in a while, so it's off the list. Also Elixir being a declarative layer over SQLAlchemy seems a little strange now that SQLAlchemy got it's own declarative layer, so it's off the list.
I implemented a basic model layer for my web application using both SQLObject and Storm, so those two I actually sort of grok now. The first major difference is that Storm requires writing some raw SQL to create tables and related schema stuff, whereas SQLObject tries to hide SQL even for those tasks. The second major difference is that Storm separates object creation from persistence whereas SQLObject combines the two to some extent; this can be good or bad depending on what your application needs to do. Also, coming from a "raw SQL" background, both Storm and SQLObject have some "issues" when it comes to formulating complex queries. Nothing much to be done about that I guess, but I still don't like it all that much.
If I had to pick an ORM right now, I'd probably pick SQLObject. But I have a few more to evaluate so stay tuned. :-D