You could try swaying the conversation your way. Talk about things you want to talk about as well. Don't worry what they're opinion will be. In fact, don't worry about anything you can't change.
I've been in this situation before, staying quiet whilst everybody talks. But this was at school, where I wasn't overly confident or popular. After school, I eventually drifted from those friends, made new friends and started to feel more comfortable in social situations.
And I agree with other posts, definitely practice practice practice!!!! Just go out, all the time, anywhere, with friends. Get a best friend, a wingman