Due to the incessant swarm of complete and utter nonsense that has been forcing its way into Firefox over time, I've decided to start collecting my personal list of “must-have” about:config tweaks required to turn Firefox into a functional brower.
NOTE: Unfortunately this is somewhat out of date. The comments link to some resources that may be more up-to-date. Patches welcome.
These can be used for nefarious purposes and to bypass access restrictions.