Mostly here, other then google, and vendor closed stuff.
The number of accumulated posts here about well, everything, is amazing.
Other then learning about the unix/unix like operating systems internals, these forums offer real nice programming best practices, language agnostic.
A great place, feels real friendly and close, unlike most communities on the internet.
Human approach, patience, straightforwardness and professionalism makes this number 1 site.
Keep up the good work
Regards
Peasant.