Fast and affective teeth whitening?

What is the cheapest, quickest way of whitening severely stained teeth when brushing alone doesn't help? Are there any products on the market that ACTUALLY work and works fast?
--------------------
If your teeth are severely stained, you need to get them cleaned professionally. The cleaning will remove much of the stain, and you can speak to the dentist or dental hygienist about your options of whitening. This doesn't mean that you have to get a professional whitening from them (it's very expensive), but you can ask them if your teeth would accept whitening. You may have staining caused by an abnormality that occurred while your teeth were being formed; if this is the case, you would have to ask the dentist about options you have to make your teeth look whiter, or he/she may suggest veneers. It's better to have a professional cleaning and ask their opinion on what you can do than to rush out and buy whitening products that can cause sensitivity that may not even work, and if they do, they're probably just going to mask the problem for a short time. If you do see a professional and they say you could accept whitening, I know that crest whitestrips worked for me when I was getting married, but I did the ones that took 2 weeks. I had really sensitive teeth when I was done, but I know that if you get the ones that take one week you're going to have VERY sensitive teeth and it's not comfortable at all. Just before christmas, I was able to get a mouth tray that conformed to the shape of my mouth and a whitening paste that had fluoride in it. The paste didn't cause any sensitivity whatsoever to my teeth, and the tray was cut so that the whitening product didn't touch my gums and cause pain (which the crest whitestrips go right over your gums, which make them sore). Of course, I got this mouth tray and whitening paste from my school and it was free for me, but it worked great. Some dental hygiene schools will offer whitening for very cheap compared to dental offices, so that's another option. Good luck to you, I hope you can find something that works!
Source