Cobian Backup 5.2.1

Not all backup software is expensive, complex, and time-consuming: this one is free, ridiculously simple and satisfyingly speedy. It's also more powerful than either the price or interface suggest; multithreaded, installed as either an application or service depending upon your needs, and able to back up to an FTP server for secure offsite storage.

It compresses using the ZIP algorithm, supports incremental backups, uses file masking, and gives you the ability to open/save lists with different backup sets. Don't expect continued development or instant support - the author has made it open source, but do expect it to just work in the background without eating system resources.