I'm planning on converting a Nikon D50 to dedicated infrared, replacing the internal IR cut filter with one that will block visible light, and pass infrared.
Google has turned up a couple sites, and ebay has one listed. I'm wondering if anyone has done this, and can recommend one (or recommend against one)
You don't state which country you live in but Lifepixel is very popular in the states and probably do the widest range of conversions.
In the UK there is Advanced Camera Services, which are highly regarded but pricey and Protech which are a bit cheaper. I had a 450D converted by Protech (720nm) and was very satisfied:
If you don't already have the Nikon, consider buying a Sigma DSLR - either the SD-14 or SD-15. They have an IR cut filter that doubles as a dust filter, that is really easily removed and put back in.
With the cut filter removed the camera is fully IR, you can then add something like a Wratten 89b filter to the lens to get the traditional IR look, or shoot a kind of "full color" IR.
You can probably get one of those cameras for less than the cost of conversion alone.
The earlier Sigma DSLR's also did IR, but the resolution is not as high and the dust filter required a screw to be undone to be removed, instead of being able to remove by hand.
I can put in a good word for LifePixel. I converted my Canon 20D about 18 months ago now... I actually did the conversion myself and I can attest to the quality of the tutorials they provide. Walked me through every step of the way and I had no issues whatsoever.
Of course if you're not into DIY monkeying with your camera, they'll do the conversion for you. I had a friend go this route and also has had no complaints.
Look for Lee Polyester IR filter material. It is inexpensive and works just as well as any glass filters I've ever used. Accurately cut a disk of it to fit into the mount of any inexpensive UV filter you might have laying around, ensuring it is a close-enough fit so that no visible light leaks around it when the filter's retaining-ring is put back in place. For about a $14-$25 investment you can make a $100-$250 filter for yourself.
When stacked with a Wratten Green filter, this works exceptionally well with any of the Sony cameras that have their "NightShot" mode in them, to bring the IR light levels of daylight and sunlight precisely within range of their restricted shutter-speeds used for nighttime IR photography.