Get those ditties offline! Use VLC Player to transfer your mp4, avi and mkv files from your desktop to your iPad. Connect your iPad, open up iPad within iTunes, select apps, scroll down to vlc app and add media.
Fun side note - when your not physically connected, you can grab files off of your Plex server through the vlc iPad app and download to device without having to purchase a Plex pass.
- not necessarily your question but I was stoked when this worked.