The TP forums are worth keeping an eye on once you qualify for access. Just remember that there are rules for using these forums, they don't necessarily offer "bargains", and you won't get any warranty with a private sale.
The dealers mentioned in the previous posts all have websites, and most of them update their inventory quite often. Compare their prices for anything you're interested in. They all offer some sort of warranty too. My friends in the US speak highly of KEH, and I believe they rate their gear very conservatively, but the additional costs for international shipping and any potential returns might make them too expensive. Have a look anyway?