Remove the IR filter from the image sensor? I remember doing this on an old Fuji Digicam. Used to use a piece of exposed film negative to filter out visible light. The resulting IR photos were awesome. The Fuji camera displayed IR as a bright pink colour, but set it to black and white and pictures were really cool.
HWY 401 at dusk
Weeping Willows (foliage is really green)
OT heads up: New phone cameras like the new iPhone DO NOT use a physical IR filter, the IR is filtered out by logic. The reason is so that the iPhone can gather an (more accurate) IR image of your face for biometric purposes. Also, they plan to use it for DRM/Censorship where IR light pulsed from emitters at a live event (concert, crime scene [cop car light bar?] etc) that will instruct the camera device to disable (lock out) video recording without the user being able to detect the signal.