Some of my work as an image engineer in the R&D branch of a machine vision camera manufacturer is about how to filter the light.
In this machine vision cameras the filters can be changed mostly without opening the camera body. The reason why the customers want to have a filter with infrared transmission are manifold.
But I suppose mostly not to create some kind of art.

For those who want to create more artistic pictures than, lets say a sorter, a DSLR or a compact camera would probably (not for sure) be better.
How one can create infrared pictures - technically spoken?

These are the main ways:

1. You take a normal camera and put a filter in front of the lens

2. You take a normal camera and take an infrared-pass filter somewhere between lens and mirror (DSLR)

3. You take a modified camera without IR-cut filter inside
3.1) You have the original IR-cut filter replaced by some kind of an IR-pass filter
3.2) You have the original IR-cut filter replaced by some kind of clear glass
3.3) You have your IR-pass filter in other places than the original IR-cut
3.3.1) You put your IR-pass filter in front of the mirror
3.3.2) You put your IR-pass filter in front of the sensor - but behind the mirror

The ways 1 and 2 have in common that the camera is unmodified, even the warranty stays unharmed. But you loose a lot of light because of the use of an IR-pass AND an IR-cut filter!
So you get very long exposure times, I do not know a camera wich could be used handhold. Probably the older Leica M8 with the bad IR-cut filter inside?
Furthermore you see nearly nothing in the viewfinder (DSLR).

Way 3 has nomaly the problem, that the camera has to be opend (not the Sigma SD 10 and 14) - so you loose your orignal warranty.
But in most cases you have short exposure times, handhold photography is possible.
With 3.1 and 3.3.2 you have the bright viewfinder (DSLR)
With the 3.3 ways you have the way to change the filter without high effort - I know only two kinds of this ways: The one is the Clip-Filter system, the other one is my modification with the filter directly in front of the shutter.

Here are some ways to get an infrared modificated camera - or how to choose the right camera and filter for infrared photography:

My own kind of IR-modification - you can change the filter easily - EOS 350D / Rebel XT

Thomas Westerhoff instructions how to changing the filter in a Canon EOS D60

Achim Schaller: EOS 10D filter change

Tim Cann modifiys a Canon EOS 20D for IR-photography

Bob McCourts modification of a Canon EOS 40 digital SLR

Christian Buil 's exact manual how to modify a EOS 350D / Rebel XT

loglouis / disassembly of a Canon EOS 1Dd Mark III to the IR cut filter

Christian Buil ones more about the EOS 350D - but now the autofokus adjustment - it is french, but cou could see how it is done

The "Balkonsternwarte" with their Canon EOS 350D modification

EOS 350D astro modification, Henning Nöldge

Astronomic EOS 350D,

One more EOS 350D,

EOS 350D / Rebel XT for astronomy modified - with special filter and a peltier cooling! Guido Küppers

Javier Gómez Laina & José Luis Rey writing about their 350D conversion

Ashley Roeckelein page about the modification of a EOS 350D / Rebel XT

Levin Dieterle's site with the conversion of a EOS 350D as a astro camera (with special filter instead of the IR-cut)

Curt Walkers mod of a Canon 350D / Digital Rebel

Rainer Hönle has some data Seite about the original IR-cut and anti aliasing filter

Gary Honis homepage with his classic Canon EOS 300D / Rebel infrared modification and some more here

Donald Schwab baut eine Canon EOS 300D auf einen Baader IR Filter für Astronomie um

Sylvain Weiller build a tool to extract the IR-filter of the Canon EOS 300D out of the frame

Terry Lovejoy altert his Canon 300D for astonomy

Gary Honis retrofits the filter in a Canon EOS 450D / Rebel XSi and 1000D / Rebel XS shows how to tinker on the Canon G1 und G2 Powershot compact cameras and some useful information for everyone

Chun Lo modifys a Canon Powershot G2

Deadpixel @ wrote something to his Nikon D70 / D70i infraredphoto conversion

Christian Buil change the filter in a Nikon D70 to increase the IR-sensitivity

Nikon D70 infrared optimisation , Michael Kunze

Eric Boutilier-Brown wrote about the focus correction on his IR converted Nikon D70 or here on his own site

MagicNikon on fredmirianda shows the conversion of a Nikon D40

Pablo at Some hints, which cameras are usable for IR photography - I suppose which asre sensitiv without modification

Infrarot-Forum - a good source about IR-Photography, in German

Kobold_IR from the Infrarot Forum about his conversion of a Canon Powershot S5 IS, in German

Sony 707 disasembly and filter changing

Sony Alpha 100 infraed conversion , Dragos

wbicher from the german Infrarot Forum about his simple Canon G1 Infrarot-modification

Stefan R. Hübner about his Canon S5 IS IR tinker work

BeyondRED wrote about the inrared modification of a Canon Powershot G3 and nearly the same here

Kobold_IR at wrote about changing the filter of a Olympus E-410 and here on his own site

Kobold_IR wote on about the modification of a Olympus E-300 and ones more here on his own site

Frank Gähler describes his FourThirds IR moficication of an Olympus E-420 with Edmund Optics plastics filter

Jens Birch upgrades a Olympus E1 for infrared pictures Canon IR-compatible lenses

Sojourner on DPReview about how he tinkerd his Fuji Finepix 3800

Sony NEX-7 Infrared conversion

Nikon Coolpix 950 and 990 enhanced for IR-photography, here too, James Wooten

Transmission of the filters from a Nikon Coolpix 950 and a 990 infrared-cut filter - but I think uses filter with more than 70% transmission

Nikon Coolpix 3100 NIR Hack , elrobis

Jens Roesners improvement of a Olympus Camedia 2040 rangefinder as a IR-Cam

Fuji FinePix 1300 IR Modifizierung , Mark Hoekstra Infrarot cheapy

Jens Roesner: IR filter reccomendations

Thomas Koehler upgrades his Pentax *ist DS for IR

Sean Carpenter modifys his Pentax *ist DS without cutting the cables

Vincenzo Micelis infraredmodification of a Pentax *ist D - these Pentax cameras have noting glued like the Canon EOS 350D !

Jens Roesner: Pentax *ist DSLR modification - done by Pentax!

Jens Roesner refines a Minolta 7x to take ir shots Infrared-usability of Nikon cameras and lenses (Hotspots..) - performs infrared modifications for customers, but shows also how to to it by yourself:
Nikon D50, D70, D70s, D100, D1, D1x, Coolpix 995, Coolpix 5400.
Fuji FinePix S3 Pro
Canon 5D, D60, 10D, 20D, 350D / Rebel XT, 300D / Rebel, Powershot G3, Powershot G5

Optik Makario, is also a commercial vendor of ir conversions, here some reference picture gallerys

LeZot infrared conversion services

Spencerscamera is also a conversion service

DSLR Astro Tec modifys customer cameras

Baader Planetarium, a further provider of IR-conversions, and filters

David Burren: Special SW-RAW Konverter for IR-modifieyd cameras - but since january 2007 in beta testing

David Burren wrote about different IR-filter-options, in respect to normal IR-cut filters

Transmission spectra of a bunch of infrared-pass filters (Kodak Wratten 89B,88A,87,87C,87B,87A, Schott / Heliopan RG695,RG715,RG9,RG780,RG830,RG850,RG1000, Hoya R-70,R-72,RT-830,IR-76,IR-80,IR-83,IR-85,RM-86,RM-90,RM100, B&W 092,093,094),

Gerd Neumann provides Clip Filter, these are fast changeable and are mounted in front of the reflex mirror - but for Canon the EF-S lenses couldn't be used with that

Maxmax does also provides IR modifications and sells some IR transmittance filter

How to cut glass - wikiHow

With Sigma SD 10 und SD14 one can change the ir-cut filter easyly (Gisle Hannemyr)- they are in front of the mirror!

The Fuji S3 Pro is a NIR camera

The Canon EOS 20Da - a IR-camera too - and I suppose the first DSLR with Liveview

Good Pictures:

Lloyd L Chambers has some great Ir-Photos and some hints - but nothing for DIY

Horst Fischers links to good infrared photographers