It depends on what you are after here. It is possible to get the Lee/Dracula type (canines), or the Nosferatu type (incisors), or even the Interview with the Vampire type (doubled).
Also, there is a choice between simple dental caps (you might swallow them) or those with a bridge (tend to make you lisp until you get a lot of practice): another choice is a thin veneer that fits over the front of your teeth..
They are not usually suitable for eating with, or even getting too drunk with. Also, the cheaper home made types suffer from the colour being inappropriate and so professionally made ones are always better. You might try your local dental technician (dental repairs - Yellow Pages) since they are often quite keen to do work which is both theatrical and original, plus they will make an effort to make them comfortable and colour matched. An alternative is to get fully cemented caps, but consider whether you can carry that off as a permanent modification.

Bloodredfx Robbie Drake is a UK based "Fangsmith" who has worked extensively for Film, Tv and individuals - also does lots of effects work
CustomFangs is UK based and produces custom moulded fangs. Now is branching into effects generally.
Gothic is a UK based online store which offers custom made fangs along with loads of other stuff.You prepare the moulds and they finish.
Angel's fancy dress is a UK shop based in London which sells budget DIY fang kits plus loads of costumes
Sillyjokes UK based (when you need something silly!) produces a range of inexpensive teeth and fangs and carries some surprising effects as well.
Nightmare Factory US based, sells Scarecrow caps along with costumes and props.
Dr Smoke Custom made, dental fit, vampfangs along with other, theatrical stuff
Dnash - acrylic teeth by D Nash US based - lots of styles Myspace
Vampirewear Us site selling custom fangs plus lotsof other useful stuff
Gothic Studio FX A US based website offer a DIY kit. Lotsof other effects as well.
Morbid Masks - a whole variety of latex masks and prosthetic devices, some budget fangs as well
Psychic Fangs - Dental caps from Vincent "the Vampyre" Psychic-US site with DIY kits available

I'm a fang maker from Connecticut,
operating on one simple predicate:
to make you the fangs
for which you heart most pangs,
with the highest example of etiquette.....