PHP Tarbackup is a simple class that allows backing up an entire Web site. It automatically works around timeout limits by splitting the job into multiple requests, allows tarball archive creation and updates, and comes with the Veloce script, which is very useful to automatically unpack tar.gz archives remotely and skip long waiting times due to FTP uploads.
Kheops is a PHP source repository for small to medium sized projects. Its aim is to be easy to use but powerful. It features a Web interface, automated archive creation, and other enjoyable features. It works with a Python client to allow advanced users to keep a copy of the sources updated.