Meetup.com is the best way to get started. Meetings last two hours, which works out well. And you're right, keeping interest (and focus during discussions) is difficult. One way I've addressed that is to have demos or discussion topics. For example, we spent multiple meetings going Jonathan Edwards list of IDE's and programming environments throughout history. That was a surprisingly fertile locus for discussion. Expect things to start small (in the beginning it was often just me and one other person) but it will grow.