ok so i have actually been using this setup for some time now, but i thought i would pass on the idea to anyone that has not heard of it.
if you don't know about dropbox check it out here:
here (yes i do get more storage if you download from that link). The idea of dropbox is that it is just a simple shared folder that resides out on a server that will auto-update as soon as a connection to the internet is found. You can get 2gb for free and then if you need more you can upgrade to more. This becomes an awesome tool for us in the carupter scene, because it lets us copy out new music to the car without having to take the mini out of the car into the house. Ever since the iphone 3.0 software dropped, this has become even easier to use. With the native tethering support in the new iphone OS, it is super easy to connect to the mini and connect to the internet.
I started using this and man i cannot imagine going back to usb drives or yanking out the mini to update my music collection. I am using NASair as my front end, and i have wrote a nice feature that will let you point NASair to a specific folder (your dropbox folder) and it will check for new music and then automatically copy that music to the correct folder in your music folder and then update your music collection. So this just really makes everything so much easier for me.
Anyway sorry for the shameless promotion of my frontend and for more storage in my dropbox account, but no matter what frontend you use, dropbox is pretty good way to get your music back out to the car.