MacPerl
MacPerl is just so useful that a copy is almost a must. Unless you intend to run MPW it is the best way to get a powerful scripting language on your Mac, with the added benefit that all your learning on Mac Perl is useful running Perl on your server, or vice versa; with a little care you can even run the same scripts on Linux and the Mac, the major difference is that you don't pass arguments on a command line and the directory separator is different. MacPerl also comes with a neat little tool called "Shuck" for reading the Perl documentation. I find Shuck so good at flicking between the various pages that I use it even when I'm writing for Perl online.
The number of things I use MacPerl for is endless. Renaming files, deleting resource forks from image files, moving files. I also use it to search file servers for documents. When you have multi-gigabyte file servers (that you don't want everyone in the organisation to index for Find-By-Content) a short Perl script can open every document and search for occurences of a regular expression.

