I've personally been using DropBox for nearly a year now and it's really lived up to its hype. My USB drive has been collecting dust because DropBox allows me to sync my files across all my computers (works with Macs and PCs) and even allows me to create public links to share files with friends!
DropBox is FREE if you only need 2GB, which is perfectly adequate for documents and work/school type files. This is not a TRIAL offer - it's FREE and it doesn't expire! If you need 50GB, it's only $9.99/month and 100GB is $19.99/month.
DROPBOX 2GB FREE ONLINE STORAGE AND SYNCING DEAL