Who to Send to Conferences.
If you're trying to hire software developers (and who isn't?), then local developer conferences (and even meetups) can be really great recruiting opportunities for you. Mozilla, npm and IBM have done pretty well for themselves at CascadiaFest and JSConf in the last year.
To a degree, this depends on who you send to the event. At a developer conference, attendees probably aren't particularly keen on talking to another recruiter; but many would be open to hearing front line stories about your deployment process or upcoming projects. Send members of your technical teams to developer conferences.
Don't send jerks or dudebros. A few months ago, I was at a SeattleJS meetup and happened to be sitting near two fellows from a large and well-respected company. One of them (who really had enough salt in his hair that he ought to have known better) was fooling around with his skateboard in the office meeting space. He insisted that his colleague "video my kick flips"; and inevitably smacked other peoples' chairs when he lost control of his skateboard. Don't send that person. Send your outgoing and thoughtful developers, who can talk in detail about your organization's work without insulting other technology choices.
Do remember to compensate your people with time off if these events fall outside normal working hours. Your developers shouldn't have to do free recruiting work in their off-hours.