I've used ns2 a fair amount for my research work. To make life easier for others learning this tool, I recently put together a presentation on how to get started with ns2 for 802.11 simulations. This also forced me to make my miscellaneous scripts and tools available to others. If you use any of these scripts and have any problems, or if you have any other useful tools to contribute, let me know and I'll add them to my collection.
An HTML presentation using the S5 tools about how to use ns2 for 802.11 simulations. This steps through a simple example scenario and uses my tools to process the output.
A collection of scripts for processing ns2 trace files and plotting the output. Some are command line tools, others are modules that are usable from Python scripts. If you have any other tools which might be useful, please let me know.