I found that going to talks and events to meet people can be extremely effective. I love living near a university, for example, to go to public colloquia and talks — you meet the most interesting people there, who often share the same interests as you. Going to a Papers We Love talk [0] can be a great opportunity as well.
Of course, this is really only available to people who live in a large metropolis, particularily if you live in the Bay Area (if you're interested in science and technology in particular).
[0] http://paperswelove.org