Books mostly, I am building quite a library. The net is used more and more though, sites like ARC and hyperscale are pretty usefull, This forum is a good source of info too, there is always someone out there that knows that little thing you've been searching for.
I now only buy mags that have at least a couple of articles I know I'll want again in the future, used to by FSM and SAM, SAMI etc all the time, but I was getting far to many, so these days I'm more selective.