PHP Shell is a shell wrapped in a PHP script. It's a tool you can use to execute arbiritary shell-commands or browse the filesystem on your remote Web server. This replaces, to a degree, a normal telnet-connection. You can use it for administration and maintenance of your Web site using commands like ps, free, du, df, and more.
Grml is a live system (live CD) based on Debian. It includes a collection of GNU/Linux software especially for system administrators and users of texttools. It provides automatic hardware detection and its default shell is the zsh. You can use it e.g. as a rescue system, for analyzing systems/networks, or as a working environment. It is not necessary to install anything to a hard disk; you don't even need a hard disk to run it. Due to on-the-fly decompression, it includes more than 2 GB of software and documentation on the CD.
Viewglob is a filesystem visualization add-on for Bash and Zsh. It tracks the command line and environment of any number of interactive shells (local and remote). A graphical display follows the currently active terminal, listing the contents of directories relevant to its shell and highlighting file selections and potential name completions dynamically.
rrs is a reverse (connecting) remote shell. Instead of listening, it will connect out to rrs in listen mode. The listener will accept the connection and receive a shell from the remote host. rrs features full pseudo-TTY support, full OpenSSL support (client/server authentication and choice of cipher suites), Twofish encryption, a simple XOR cipher, plain-text sessions, peer-side session snooping, a daemon option, and reconnection features. It is known to compile and run under Linux, FreeBSD, NetBSD, OpenBSD, and QNX.
Mail2sh makes it possible to carry out shell commands by email. Email is sent to a particular user on your host and the commands will be carried out if the user and password given matches ones in /etc/passwd. Commands are executed with the user's privileges, and combined with a PGP module ensures a certain level of security for use. Note that the system is not natively encrypted, so use of an encryption mechanism is highly recommended for security reasons.
Wapsh allows users to login to a Unix workstation using a WAP-capable mobile phone. Features include shortcuts (to save phone typing), input of control and other special characters, command history, and searching and scrolling through long shell output. Wapsh automatically adapts to the main WAP browsers (UP and Nokia), and uses configuration files to further tailor the system for specific phones. A corresponding HTML (Web) interface is also included.