I'm looking to sell my bike, which I bought less than a year ago. It's Marin Fairfax 2011, size 15''. The model fits both paved and unpaved paths, and it served me very well during this year - both in and around campus and for triathlon training. It is in a great condition.
Technical details can be viewed here: http://www.marinbikes.com/2011/bike_specs.php?serialnum=475.
The original price was $529, and I added $30 for a rear rack, $35 for a bag that suits the rack, and $100 for a lock. I'll be happy to sell the bike together with all accessories for $500 or the bike with the rack only for $400.