I think you're in exactly the right place. Except for the description of the bike I dragged out of the garage, I was in exactly your shape 4 years ago.

There is plenty of advice on here to help keep you going, but here are my 2 cents: don't underestimate the power of vigorous walking to start getting into shape. Load up your iPod with good music, grab a dog if you have one, and take off on energetic, hour-long walks. If you're coming from zero fitness they will really help. If you're starting to ride a bike and getting sore on some of your initial rides, it's a great way to balance things out.