This sounds like exactly what you want:
http://www.basegear.com/mountain-hardwe ... zip-t.html
The MH Transition top. I have the half-zip and the tights (which are trim-cut pants and not really tights), and I love them. The fabric is Gore Windstopper softshell, and it's extremely thin and light. But, it's 100% windproof, durable, highly stretchy, and deals well with light rain.
I've worn this on many bike rides from 30º to 70º, with nothing to a light wool or Capilene layer underneath and by putting on a heavier underlayer I plan on riding and climbing well into the winter with it. It's my most versatile piece of clothing by far.
Note that it's cut like a shirt. If you want to fit fleece under it you'll have to order up a size.