HTTrack is an easy-to-use offline browser utility. It allows you to download a Web site from the Internet to a local directory, building recursively all directories, getting HTML, images, and other files from the server to your computer. HTTrack arranges the original site's relative link-structure. Simply open a page of the mirrored Web site in your browser, and you can browse the site from link to link, as if you were viewing it online. HTTrack can also update an existing mirrored site, and resume interrupted downloads. WebHTTrack is a Web-based GUI for HTTrack.
rsync is a replacement for rcp (and scp) that has many more features. It uses the "rsync algorithm" which provides a very fast method for remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand.
UDPCast allows to send data simultaneously to many destinations on a local net. This can for instance be used to install entire classrooms of PCs at once. The advantage over using other methods (nfs, ftp, whatever) is that udpcast uses Ethernet's multicast abilities: it won't take longer to install 15 machines than it would to install 2. The tool comes with a busybox bootdisk for easy loading of the tool. However, udpcast can also be started from the command line of an already installed system, and can be used for other purposes than just system installation.
rdiff-backup backs up one directory to another. The target directory ends up a copy of the source directory, but extra reverse diffs are stored in a special directory so you can still recover files lost some time ago. The idea is to combine the best features of a mirror and an incremental backup. rdiff-backup can also operate in a bandwidth- efficient manner over a pipe, like rsync. Thus you can use rdiff-backup and ssh to securely back up to a remote location, and only the differences will be transmitted. It can also handle symlinks, device files, permissions, ownership, etc., so it can be used on the entire file system.
changedfiles is a framework for filesystem replication, security monitoring, and/or automatic file transformations--essentially any application where you'd poll files or directories and either do something to them or send them somewhere else (or both). The difference is that the kernel tells you when they change instead of you having to poll. It's an easy real time FTP push mirror to one or multiple sites. It's also a full fledged MySQL client, so you can do realtime database operations (for example, batch imports). It consists of two parts: a kernel module (works with Linux kernel version 2.4) which reports to a device whenever a file on the filesystem changes, and a daemon which runs in user space and can be configured to do almost any action when a change to a file matching the one of the patterns it looks for is reported. The kernel module is SMP safe and has been tested on Intel, PowerPC, and Alpha.
rsync-bc (rsync backup client) is a stripped-down version of rsync. The idea behind rsync-bc is to provide a simple client that only supports sending data. Receiving, local file transfers, and daemon/server modes have been disabled. No destructive file operation functions will be present in a binary.
apt-got is a customizable mirror engine. It works like a highly specialized proxy. It employs several pluggable modules that are customized for specific jobs. The first available module builds and supervises a partial (or full) Debian mirror which is populated on-the-fly by apt-get requests. There is also a simple mirror module that can be used to mirror source directories or even (static) Web pages. For increased performance on already-cached files, it employes its own Apache module. It supports customized mirroring algorithms.