I wrote about it on the Paste blog but I thought I'd note Paste Deploy here as well (release page). It's still a very young project (like three days old), but I'm feeling optimistic about it, and in various forms I've been thinking about it for some time.

Basically it's a way to configure WSGI applications. For applications that support this (or where you write some very minimal glue) you could do things like this (note that I haven't made any of these Paste tools available yet, this is an example only):

[DEFAULT]
admin_email = me@example.com

# pipeline puts some filtering middleware in front of an app
[composit:main]
use = egg:Paste#pipeline
pipeline = login urldispatch

# Put one login system in front of entire site
[filter:login]
use = egg:Paste#login
database = mysql://localhost/userdb
table = users

# Then this passes different path prefixes to different apps
[composit:urldispatch]
use = egg:Paste#urlmap
/ = static
/cms = filebrowser
/blog = blog

# a very simple app...
[app:static]
use = egg:Paste#static
document_root = /home/me/htdocs

# this puts the auth in front of the app
[composit:filebrowser]
use = egg:Paste#pipeline
pipeline = auth filebrowser_app

# the login filter should give us a username; this just restricts
# who can access
[filter:auth]
use = egg:Paste#auth
require_role = admin

# this application is distributed 
[app:filebrowser_app]
use = egg:FileBrowser
document_root = /home/me/htdocs

[app:blog]
# In this case the app isn't distributed as an Egg with
# entry_points, so we manually create a glue function blog_app  
paste.app_factory1 = myglue.apps:blog_app

Well... that's a fairly involved configuration, really. You can move parts of this to other files fairly easily, substituting config:config_file.ini for the references to sections (blog, static, etc). While many of the pieces (like egg:Paste#auth) don't work now, they will very soon -- many of these things exist in Paste or elsewhere, and just need a configuration shell. There's a few other outstanding issues, but I'm very optimistic.

I'm also optimistic about breaking Paste up into smaller chunks that are easier to integrate into other projects; this package is my first attempt at distributing one piece of the project in isolation.