When you do "apt-get install" where are the .deb files stored?

They're stored in:

/var/cache/apt/archives/

unless you've issued a:

apt-get clean

Maybe you just need:

apt-get download mypackage1 mypackage2

it will download given *.deb files to the current directory. No need for root.

If you had already issued

apt-get clean

you can take a look at these pages to learn about replicating the same package configuration on the other machine