Possibly the best deal I've found so far for electrifying a bike can be found here:
http://www.jvbike.com/crystalyte.htm
You can outfit your existing or other bike with up to 500W (the legal limit) of motorized power, which should be enough to get you to work! It claims 20+ miles per charge, but I think that's if you're not pedalling much. You might be able to squeeze 35 miles out of it, if you pedal enough and go easy on the throttle.
Alternatively, you could get a small 50cc scooter which would easily have enough range to get you to work and back, though you forego the health benefits.