Two choices:

Either select in the settings of Faster Application Manager to not clear the cache after installing, and take them out of the directory /var/cache/apt/archives (as root, obviously) or, my preferred method, do just that by hand by issuing (either with sudo or as root) apt-get -d install <package-name>.

That last method prevents from having to find out which package belongs to what, provided you keep your cache clean and move files right after you download them. apt-get -d install downloads to the same location.

Edit: after looking at the reactions above, perhaps I misunderstood your post completely.