I have a bike I will be selling, but it's too big for your gf.

Couple other ideas of places to post your wanted add also might be:

Terry Bicycles web page, they have a forum and for sale section
http://www.terrybicycles.com/

Bike Forums
http://www.bikeforums.net/

LBS or local independent bike club's sometimes have free ads

Craig's List or Ebay

I usually end up paying full price for my stuff, then end up seeing the great deal after I've spent my money *sigh*. Good Luck!