With the advent of flup 1.0 and the disappearance of the middleware modules (I don't think anyone really cares about Publisher ), I've been getting a few queries here and there about alternatives.
Rather than continue to answer people individually, here are some alternatives to flup's middleware and publisher modules. However, they represent alternatives that I've personally chosen. (And considering how far removed I am nowadays from the world of Python web development, take my choices with a grain of salt.) Suggestions for other alternatives (alternative alternatives?!?) are welcome.
For users of flup's SessionMiddleware, I recommend Beaker. Switching over is a simple matter of changing the environ key from 'com.saddi.service.session' to 'beaker.session' and ensuring that session.save() is called before the WSGI application returns. (After you've appropriately swapped out flup's SessionMiddleware with Beaker's in the WSGI stack, of course.)
GzipMiddleware and ErrorMiddleware have analogues in Python Paste.
flup's Publisher is probably most like Colubrid, though I haven't personally tried it. (Also remember that flup's Publisher was inspired by mod_python's Publisher, which was apparently inspired by Zope's ZPublisher ).
Anyway, I updated the old flup 0.5 branch and uploaded the source distribution to the Cheese Shop. I really don't want to maintain two branches, so consider this 0.5 release final.