^^^For the last couple or three years the above only applies if you're looking for the most inexpensive entry level sets. mfgs. release special decontented "Black Friday Specials" and there are usually great deals on things like 50" 720p plasmas. Mid to high end models are not discounted much if any, although there are sometimes attractive finanincing deals.
If you want the best price on a good set, discontinued models at model changeover time are your best bet, as Tazishere stated, but you run a high risk of losing availability if you wait too long. Panasonic has reduced production this year specifically to avoid lots of leftovers next year when the new models come out.
I've been selling tvs for 6 years now and have seen the trend away from discounting on regularly stocked mid to high end sets take place. Also, most retailers are now suspending price matching during the BF weekend.