More recently they split this database into speed-tagged files, and introduced individual warning sounds for each of the files. These sound files don't work for the Palm or Go versions of TomTom, however they have published info on a solution that requires you to replace one of the files on the SD card.
For PocketPC TomTom v3.07 and CheckPOInt, the instructions are here.
Corrections to the database should be emailed to Cameras [at] PocketGPSWorld [dot] com. If you're just updating the speed, then just list the camera ID, and the speed. To add new or correct existing cameras, instructions are included in the download file, or available from this forum post.