I bought a 2500 HO 6 Speed QuadCab LWB SLT in August. I went in on August 31, at about 6:00 PM. Some say that helps, in my case it was chance. I honestly had no intention of buying a truck that day, I just wanted to see what the prices were.
They had my truck sitting on the lot, they said it had been there since the end of May. It had some hail damage (not bad at all) and they said they needed it off the lot. The truck is not fully optioned, but it is very nice. It has the Infinity stereo with steering wheel controls, leather steering wheel, premium cloth seats with electric driver's seat, power mirrors with electric heat, trailer tow group, fog lamps, etc. They even tinted the windows for me for free.
They pulled out the invoice, not the one they typically show the customers but the real invoice. My dad used to run a dealership, there is a difference in some cases.

Anyway, the invoice said their cost was $32k and some change. I have since confirmed that the invoice price was correct via Edmunds.com. In fact, the Edmunds figure came out higher than what they showed me, either Edmunds was off a little, or possibly the cost of the truck has gone up.
We sat and talked about it, basically he said "I'm not going to jack around, I'm going to go ahead and give you the low price right now". I figured he was playing "salesman", but he wrote down $26,135 and I walked out with a new truck.
Keep in mind that I'm not the type that cares about 3 or 4 dents in the hood and a few on top of the cab. Some care, but as long as the thing runs good and does what I need I don't care at all about a few dents. If you can find one like this, you can save some serious cash on one. Sticker on my truck was $36,850 or something close to that, don't have the sticker here handy.