iceweasel 12 should be in the mozilla.debian.net repo or if you are running testing or sid use the experimental repo.
Debian Mozilla team APT archive - http://mozilla.debian.net/
if you are running Squeeze make sure you have these lines in your sources.list
You can install it with the following commands:
$ apt-get update
$ apt-get install -t squeeze-backports iceweasel
For testing or sid use experimental
# apt-cache policy iceweasel
*** 12.0-4 0
experimental/main i386 Packages
Hey I am with you, I switched to using Firefox and Thunderbird way back when Debian changed the names. I have used Firefox since back in the day when it was called Firebird and Phoenix.