Other people's TDLs. I note that this year's CCC has devoted some time to the wanktank phenomenon in Germany, and also elsewhere. Volker Bilk's slides are here; it makes a lot of sense, but there's quite a bit of German philosophical maundering in there, and I'd have liked to see more case studies/howtos. As far as his call to action to map the wanktanks goes, I fully agree.
In other CCC presentations, it looks like there's going to be a lot of GSM hacking in 2010. See here, here and here.