Don -- Dropbox.com is a cloud-based file management system. You put the Dropbox client on a machine and it creates a folder in your My Documents (or indeed, your entire my documents). Every file in that folder - and in subfolders - gets synced to the Dropbox server. Put drop-box on another machine, and your two machines sync. Everytime you change a file, it propogates to other machines with the same dropbox account.
You can view your dropbox online at dropbox.com and can access files that way from machines that don't have dropbox installed. You also get 30 days of version control with the 2 free GB of storage.
ipod, ipad, iphone, and Android all have dropbox clients. Here it works differently. You go into your ipad or Droid phone or whatever, and see the list of folders, click on the file you want, and it downloads it to your device.
I have Dropbox on every machine I own (2 laptops, 1 netbook, 2 desktops, 1 Droid). I have the 50GB package with unlimited version control ($139 per year total). I no longer need to bring USB drives with me to work. All my files are on all of my machines. If I download a CD of music on one machine, I copy the files to a music folder in Dropbox, and can access it from other machines.
I was at a conference and took notes for a book proposal I was writing on my laptop, but did not have a printer. So I accessed the file on my Droid and opened it in Documents to Go, and was able to refer to it during my meeting with the publisher. If I needed to, I could easily have emailed it as an attachment from the Droid.
Everytime you refer someone to Dropbox, you and the person referred get an additional 1/4 GB. So if you want to try it, drop me a PM and I'll send an email referral to you.
Dropbox has changed the way I compute.