For similar needs, I run a small virtual machine in my windows machine. To download packages without installing you can use
apt-get download <package_name>. The command will download the package to the directory that you run the command. You can then copy the packages to the host, then a flash drive, lastly to the machine that you use.
I know this may not be the most elegant solution but at least works for me.
Oh, I forgot: If you need dependency checking, you can run
apt-get -s install <package_name>, copy the dependency line and just paste to
apt-get download command.
Update 2: I looked to the manpage of the
apt-get. It has a switch called
--download-only. You can pass this to install &
apt-get will get all the packages for you but won't install them. You can find your packages in
/var/cache/apt/archives. An occasional
apt-get clean will delete the files from the directory, so you can get the packages you want easily.
Update 3: To install the packages obtained with method in Update 2, you need to put these packages again in
/var/cache/apt/archives in the offline machine. If you want to install packages you got with
apt-get download, you can use
dpkg -i <package_file>.