Fink has been very helpful over the years—I started using it when I bought my first MacBook in 2003—but I always dreaded making the upgrade to Snow Leopard, especially after having shunned the upgrade to Leopard before. It turns out that I've been wrong: starting from scratch, it took a handful of keystrokes and 10 hours of compiling to get everything up and running again.
Inspired by Higher Order Perl, I once tackled the problem of merging several log-files into one common time-line. While the solution itself is useful, this article also discusses the iterator pattern in Perl.
Shell level access to a Linux host enables a rich universe of possibilities, even if (initially) lacking administrative privileges. If you find yourself in the situation that you have to provide access to certain applications or functions to someone who you do not trust on a moral or technical basis, a custom login shell might be one possible solution.