Professionaly, I'm using 4x5 and medium format film cameras with movements. I occasionally use an 8x10. I will probably go to a small(er) format view camera (6x9 cm) and digital back later this year (I don't see computers doing Scheimpflug in my lifetime).
For stuff like you see on this site, which I do primarily for fun and creative outlet, I shoot film in medium format. I haven't used a 35mm system in probably 15 years. Up 'til now, the technology in 35mm digital bodies has changed so rapidly (every 18 months) that I haven't had the desire to get on the merry-go-round. But I think the cycle is now slowing down and am considering a purchase. We do have a digital point-and-shoot in the family.
As far as what is most popular at this point in time, the digital point-and-shoot is most popular as far as the general public goes. Around here, I'd bet it's a 35mm digital SLR.
People who do stupid things with dangerous substances often die! -me