I love CANTER. I've seen several nice looking, smaller sized TBs on there for $500-1000. I'm working with an OTTB now who would make a fantastic lesson horse in a couple years. He is so willing and so easy.
Re: finding breeders, I've called both breeders I know and breeders I've found on the internet that are in my area. Sometimes people are holding out for top dollar for their young stock and I respect that because I know how much it takes to get a nice baby on the ground and raised up to a rideable age. However, this time of year sometimes breeders take a look at their inventory and think about all the hay they are going to be needing to get through the winter and are ready to make some very good deals, especially to a competition type home. Often breeders are reluctant to advertise young stock at low prices because they don't want to devalue their product, but a phone call from a serious person might reveal that they had some room to negotiate.