SyncToy
Microsoft’s SyncToy is a great free way to copy or synchronize files in Windows. With both a convenient user interface and a command line, SyncToy can be set to copy files manually, on a schedule, or triggered to run during events. My girlfriend’s computer is set up so when she logs in, it will copy her USB stick on which she stores most of her files to a network share if it’s connected. I use it to duplicate my important data from my file server to a large drive in my desktop PC as an on-site backup.
SyncToy has three modes for all sorts of different needs. If you find yourself copying files, or wishing you had, SyncToy might be for you.