chdist is a nice tool that makes working with different releases much easier. You can use it to poke into and download packages from different releases without setting up a chroot for each one. I use from my Maverick host to grab the source packages from Natty when trying to track down a bug.
For example, I’m looking into adding cortex-strings into the Natty libc6. Install chdist using:
apt-get install devscripts
Tell chdist about Natty:
chdist create natty
Update the list of packages:
chdist apt-get natty update
Check which version is currently uploaded:
chdist apt-cache natty show libc6
Grab the source:
chdist apt-get natty source libc6
The distributions and configuration files end up under ~/.chdist such as ~/.chdist/natty/etc/apt/.