Where to find used machinery?

I am in the market for a used excavator, track skid steer, and dump truck. I am new to this industry and am just wondering where you guys find used equipment. I have looked on craigslist, which is good but hard to search the entire state and I have a feeling the vast majority of stuff for sale is not on there. Obviously dealers are an option although I find in my area the prices they ask are certainly a premium. Machinerytrader.com seems to be mostly the same dealers. Are there any websites that are for sale by owner? I know auctions are an option, although I hesitate to go to a big huge auction since I think that is somewhat of a gamble. If I have looked all the right places that is fine but if there is any website or method of searching that I have not been exposed to please let me know!