the apt-get cache, backing up and using to install debain on another machine

["Jim Hribar" <jimhribar@msn.com>]

I used apt-get to install the packages I wanted on my Debian machine
after a "network install".  I know that apt-get caches downloads so you
don't have to download the packages more than once.  

How could I backup these "cached" packages?  Where are they? I intend
just to move them to another machine using ftp.

Additionally, I want to install Debian on another machine (I have no
CDs, just the network-install disks).  Could I somehow install Debian
(fresh) by pointing the install to my current machine and/or package
cache?

Thanks,

Jim Hribar