No clue regarding active noise cancellation. If you're okay with passive (aka, they go on your head and keep sound out just by virtue of surrounding your ear), a few popular low-cost options include the Audio Technica ATH-M50s and Sennheiser HD280Pros. Everyone in the audio world has their own opinions on this sort of stuff, but I've owned a pair of each of those and, despite their small flaws, both are decent pairs of cans.
The only time you really want the active stuff is when you're traveling and there exists a lot of low-frequency noise, such as on a train or airplane. Looking around on Hydrogenaudio confirms that the QC are okay if that's all you need, and also that alternatives exist, such as IEMs, which might have a wider range of use as they simply have very heavy passive isolation.
I brought a pair of Sennheiser PXC-450s - they are nice in that you can turn off the noise cancellation and use them without batteries (and get a boost to the sound quality by doing so), but if you are on a plane or just have loud neighbors in the office I can turn it on and cut down on the outside noise. The cancellation itself isn't quite as good as the QuietComfort ones but it's close enough.
The only time you want ATH-M50s is when you're cold and want to feel your ears sweat. I break them out on occasion for close listening to something or other, but holy crap, they're miserable. The Bose QC-15s go for hours at Starbucks while studying. I'll probably buy a pair for each of my kids when they go to college.
Shure is fantastic. I've owned countless pairs across various price levels and have never been disappointed. While I find that their top of the line SE535 break easily at the gym, their warranty service has been exception and lighting quick -- usually next day servicing.
Not sure why you got downvoted for this, other than brand snobbery. That's also been my experience with Shure. As well as Sennheiser HD650 & Fostex T20RP, I own pairs of Shure e5c and e215 in-ear phones. The e5c are getting on a bit, and are perhaps fragile, but I had custom ear molds made for them. Out of the lot, the e215 are the best bang-for-buck I've come across.
The e5c's main problem is they are SO sensitive they are completely unforgiving about the amplifier used - almost anything with a gain block after a volume control is going to have too high an intrinsic noise floor for them to not show it up.
I recommend the Bose for flying. I also had the Creative Aurvana for a while until they broke, which were decent too, but not quite as good. For just walking around town, I like my Etymotic in-ear phones, but those are uncomfortable on a long plane trip. When plugged in though, they have great isolation.
An open headphone like the HD 600 (which I'm wearing now) is really unfair to compare against noise canceling; I use Beyerdynamic DT770 for "closed", and in-ear from etymotics or ultimateears, rather than active noise canceling -- the only active noise canceling headphones I have are Pro Ears and MSA Saladin (shooting/military ear protectors which take radio input).
I'd be upset if my home environment were loud enough to warrant noise canceling, though.
If you are willing to go with in-ear headphones then a good deep seating pair of passive noise isolating headphones will kick the pants off any active noise cancelling pair.
In terms of pure isolation, Etymotic makes some of the best out there (>30dB isolation), and I think they sound absolutely brilliant.
