As far as commuting to work is concerned (15-45 minute ride), after trying many expensive options, my favourite option is.....

the dishwashing glove!

Available in multiple colours (awesome for hand signals), extremely cheap, pretty good grip, windproof, and, above all, totally waterproof. I buy it in a bigger size and wear a thin (or thick, depending on the temperature, wool or fleece) liner underneath. I fit the opening under the cuff of my rain jacket, creating a perfectly warm and cozy environment for my hands.

This works well when the temperature is between 3 and 8 degrees Celcius (35 to 40F?), which is to say most of the time in the Pacific Northwest's winter. Sweat hasn't been a problem for me using this scheme for the past two years, but your mileage may vary depending on how hard you are working out.

Other options include the kayaking neoprene glove (which I haven't tried). I was also quite successful with my red Vancouver Olympic mittens, also with a thin liner underneath, in all weather but total downpour. For some reason, despite being cheap, cotton, and wet, it would never be really cold. My husband goes for surgical gloves on top of his winter padded cycling gloves for long rides in the cold rain.