Nike + iPod Nano + Getting off my ass = (-50lbs)

So, I've gained a bunch of weight and by a bunch I mean my favorite jeans are snuggy when once they were too big. Sad, really b/c they are SOOO cute.
Why oh why are my jeans so tight?
A few weeks of deep thought and I have no idea - it's definately a bunch of stuff. Stuff I need to noodle through. Noodling seems to work better when I'm on the bike (which I haven't been) or on a walk (which I haven't done in a while).

• Gym? - $45 a month of a smelly meat market.... not so much
• Personal trainer? - $100 a session, not unless I'm losing 4 to 7 lbs per session
• Boot Camp? - not much for being part of the military...

I have an iPod, sneakers and a bike, my WW books - basically - like a free gym with a rockin' wee trainer and GEMA to remind me, "aren't those jeans tight?" Finding the little spot in my brain that holds the little "get off your ass" endorphines (I believe the techincal term is AssOffadriene) - work in progress
Nike has some interesting work out mixes on iTunes - so there is a little investment there.

SO - here is hoping that with a little will power, Nike and my Nano - let's see if I can drop 50 lbs.
Suggestions on music would be great, recipes too =)
Wish me luck