Hey,
Among the usual press release stuff we used kickofflabs + facebook advertising pre-campaign which got us around 150 followers for when we launched. If it's in your budget I highly recommend facebook ads during your campaign too, took us a while to master who to target and how to best advertise in terms of images and call to actions, but we got there eventually. From the stats on our dashboard it's paid for itself a few times over.
That gave us the push we needed to get noticed early on, but we're starting to tail off now. Will have a look at the linkedin groups, sounds like a good shout. Reddit was OK too, a friend posted for us to avoid the frowning lol
Most important bit of advice for us has been to engage with your backers, talk to them and ask questions in your comments feed. This gets them more involved with your project on a whole and they will in turn be more likely to talk elsewhere about your project.
If you fancy taking a look, here's our Kickstarter
http://kck.st/1pbmpo3I am no expert, just learning as I go. Hope this helps