I'm 21, and about 5' 10".
I started my biking season a bit weirdly this year. I'd been riding an ancient Huffy Mt. Echo I'd had since middle school starting in March or April, and for a while there I didn't want to ride at all because that thing sucked so hard. Back at that point, I weighed in (on my parents aging bathroom scale, so forgive the lack of accuracy) at almost 230lbs. The first thing out of my mouth was "Oh, H*LL NO!" That jolted me off of my a** enough to start checking out the local stores for something to spend my tax refund checks on when they came in.
Fast forward about a month. My state refund check had been in my pocket for about a week when I literally almost tripped over a near-mint condition Schwinn S25 tagged for only $75. The same bike I'd been drooling over at Target at over $250. A good sign. Cashed the check and paid. (Interesting time getting it home, though...had to stick one wheel out a window to get it to fit in the car!)
I've ridden (sic?) that thing close to 300mi this summer. As of now, I'm down to about 205lbs. Cold and snow should be approaching in a couple of months (not to mention a job...YAY!!!), but I'm still gunning by season's end for getting under 200lbs for the first time since senior year of high school. The good news is as the weather cools, I'll be able to ride to my part-time job (as a PC repairman) and still look presentable to customers. The new job should also pay enough to let me get some decent riding gear, or maybe even a nicer rig like some of you have!
May your wheels roll true, and the wind be at your back.