If a package is not available in your version of Ubuntu, it's fairly easy to backport the package from a more recent version. For example:
Let's start by installing some packages required for building any package:
apt-get install build-essential devscripts
Next we get the source packaging. In this case we go to http://packages.ubuntu.com/jaunty/python2.6 and look on the right and see three links under "Download Source Package". You should end up with a .tar.gz, .diff.gz and a .dsc file.
Next we unpack the source:
dpkg-source -x python2.6_2.6.2-0ubuntu1.dsc
This will extract everything into a directory. If you change into that directory and see if we can build it with the packages we currently have installed.
debuild -us -uc -b
This will either take some time and build you some packages in the directory above the source directory. Alternatively it will complain about missing build dependencies. If you're lucky, you can just install them and try building the package again. If you're unlucky, the package requires an updated package. You can try following the same procedure to build the build dependency or you can try changing the dependency version in debian/control. I'd only do the latter if you discover you're ending up building too many packages as the packaging hasn't been tested with those changes.
Once you've got your packages, you can run
dpkg -i foo.deb bar.deb
If it complains about dependencies, you can run:
apt-get install -f
which should sort out your dependency problems. If it doesn't, you may need to back port more packages.