+1 for dropbox - 2GB free, up to 100GB paid. Shared and replicated on all your machines, and also an iphone client, an android client, a blackberry client, and a web client.
You mentioned traveling so I think the ability to pull up a file on your phone or on a website would be a huge benefit to you. (the dropbox phone apps will preview files- I can also say from experience that you can use dropbox on the ipad to open files in other ipad apps (for example you can open a pdf in your dropbox account in goodreader on the ipad.
Best of all, Dropbox has been rock solid for me on both mac and windows. I have never had a problem with dropbox ever.