Does anyone know if there is an easy means of saving and installed application as a package so that it can be ported to another N900. I was looking for it on their website but they no longer support it so it is no longer available.

After it is installed? Not if it wasn't saved in the first place, as far as I know. If you do a new install, however, you could do:

Which will download the package only, without installing it, and the .deb can be found back in the folder

If it is not available, then it won't be in your cache...

There is dpkg-repack package, but it does need dpkg-dev as a dependency which is not in the repos.
You could grab it here from the sdk-repo: http://repository.maemo.org/pool/fremantle/free/d/dpkg/ Grab the package, that does correspond to the installed version of dpkg on your N900. Query that with Install them normally to invoke as follows:You will find the package in the working directory, which might be /home/user in my example. Adjust the package name in the command example please.