@ (monkey-tail) is a simple collection of simple commands. Built-in commands include listing of memory usage and open files for a process (by name or PID), running processes detached from a terminal, and running a program only once. @ can merge external pieces of code into itself to provide extra commands. Additionally, these "externals" can then be updated from their source. Currently there are externals available for extracting archive files (including nested archives), setting the GNOME desktop wallpaper image, and for replicating @ to another host via SSH. Externals can easily be written, as they are simply collections of Bash functions. It is completely self contained and self modifying, and is implemented in a single file.
Changing directories in bash can be tedious if you have long names or nested paths. Creating aliases or adding to the CDPATH can help, but can be improved on. Bashcd adds 6 new commands to make changing directories a bit easier. This commands use find, the locate database, the mdfind database, or other contextual information to make it easier to change to other directories.