Ever needed to monitor instant message traffic on your network? Linux.Ars has the goods on how to write a script to intercept traffic on the local network.
There are many situations where the ability to monitor network traffic can save a lot of time and effort. If you want to reverse engineer a network protocol, keep an eye on junior's browsing habits, or blackmail your evil boss, Ruby and libpcap can make it easy! With this excellent Ruby binding for libpcap, you can monitor traffic all over your network with only a few simple lines of code.
If snooping on AIM conversations isn't your thing, there's also a tutorial on how to automate image processing with the GIMP, plus an introduction to Conglomerate, an XML editor for Linux. Time to get your penguin on!
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