I'm vocal with my coworkers that I don't drink and that's why I do not attend many of the social outings. We have a lot of outings that don't center around or involve alcohol (ie. Gokarting) and I attend those. I make it a point that I'd rather they go have fun at a bar and I'll "sit this one out" rather than turning all events into "sober-friendly" events.

E:

Since it might be brought up... I politely decline offers to attend the bar gatherings and "just don't drink". I dislike being around drunk people - I find them annoying and having to repeat myself 20 times in conversation to be frustrating. Instead of ruining their fun experience with my irritated and increasingly unfriendly attitude - I stay at home and let them enjoy their time.