I have Cubase LE on two laptops, and Audacity on my desktop. The desktop is more my 'editor' these days. Honestly, Audacity is fine. You are limited to 32 tracks, compared to Cubase LE's 48, but it beats the Hell out of Ableton Live Lite's 4 audio and 2 MIDI track limits. Audacity won't do MIDI, but 32 audio tracks is plenty for me. The free LAME plug ins certainly aren't lame, and I find Audacity a breeze to use.
You get these programs free when you buy anything other than socks these days, and the Audacity program is a free download. M-Audio gives away Ableton, but honestly, it
is 'lite'. And more for looping. No thanks.
To the original question, I swap files between two laptops and a desktop all the time. Cubase LE 4 only allows exporting as a wav file, Audacity allows either wav or MP3
D), and all you need is a box full of USB flash drives. Depending on how many tracks you use, you won't even approach 1GB, so any cheap flash drive will hold at least a song or two of all separate tracks. Hell, I separate the drums into each individual track, complete with cymbals on their own track, I'll double track guitars, double track vocals, and still have tons of room on a flash drive. The drive I just looked now is new, has two whole songs on it, and I'm using less than 400MB.