People are interested in what others do but rarely take time to ask them. However Ignite shows strive on allowing people to talk and others to listen. Why is it such a success?
Presentations only last 5 minutes. What do you have to loose if that's boring? And if you like it, go talk to the speaker afterwards.
Follow Ignite shows and you'll learn a lot and knowledge sharing accessible for all. Then make your own rules for discussions and ask your colleagues to do it.
Anything goes but choose something your colleagues will like and open up locally outside your direct team. No more excuses to start sharing knowledge across your network.