Goto the market and install "Dropbox"
Download Dropbox for the PC from here
http://www.dropbox.com/
Install the PC version, set up an account (2Gb FREE Account), login
Run the Android version on the tablet, login into your account
Now everytime you want to copy a .APK file to the tablet, just drop it into the Dropbox folder on the PC, open Dropbox on the Scroll and it is instantly there ready to download and install.
Saves having to plug it into USB and mount the drive each time.