If you're just looking for an around-town beater, it's tough to beat the late-70's/early-80's Honda CX500/CX650. Bulletproof drivetrain (they are still the favorite bike of the London motorcycle messengers, which should tell you something), and dirt cheap to buy and maintain. Plus the standard seating position is great for around-town maneuverability. The one minor drawback for a novice is that the bike was engineered to be a little top-heavy, but that's not a big deal IMO.
Of course,
I'm a little biased 
