I looked at the Classified section of the local tri series and they had a lot, but I ended up finding one through the Classified section of a store website. Some bike/tri stores have websites with a classified section so customers can turn over their bikes (and buy from the store) more easily. The bike I bought was a Cervelo Dual and included computer, pedals, bottle cage, profile design aerobottle and brackets, extra saddle, and I paid less than half of the bottom line he paid new. I know this because he gave me his original invoice so I could use it for warranty purposes. It was 3 months old.
All my bikes (C-Dale F300 MTB, Bianchi Giro roadie, C-Dale Slice tri) were bought used from CL. Key with CL is that you have to meet in person to see the bike, or you risk getting scammed.