what about a simple :

this copies the debs to the given folder. of course, you have to run the command every now and then, lest some debs get flushed. it seems that this will suffice for non-programers like me, who just need to be able to re-install packages without re-downloading. (of course, all the general risks of doing things as root apply)

However, this doesn't explicitly group applications with their dependencies, but they are still there, and can be installed via

as mentioned before by others. I actually use the above method on my Debian PC which rarely gets access to Internet connection.

and, great link Drexxx