As Rik says, there's lots of useful info on here using the search engine, although sometimes it can be a bit difficult to find exactly what you're looking for!
So I'm going to weigh in with a simple piece of kit that is multi-purpose and cheap, which is the Swedish Army Trangia cook-set. For around a tenner, you get a decent meths burner, a windshield that you can also use to make a wood-fire in, a billy-can that you can also suspend over a bonfire, a lid/frying-pan/cup that you can also use in conjunction with the billy-can to make an oven. And most sets also come with a 300ml bottle to store meths in. This set is pretty much bullet-proof, although not the lightest if you're into ultra-light camping. You can find it on the internet/ebay etc, or from good surplus stores like Endicotts.
Sure there's much more sophisticated stuff around at a price that will boil water quicker, but I've used this set-up in -20C temperatures, and it's pretty much fool-proof as there's nothing to go wrong, hoses/connectors/pressurised containers that leak or blow-up on you etc. For around a tenner or so, I defy anyone to suggest a better-value bit of kit (other than maybe a Mora knife!
And Youtube provides lots of examples on how to use it.
