Interested in providing captions or audio description for a video? Here are some tools available to you:

3Play offers a variety of video-related services including captioning, transcription, translation, and subtitling.
Cost: Per minute pricing (Volume discounts available)
MAGpie Video Captioning
Provided by the National Center for Accessible Media (NCAM), MAGpie (Media Access Generator) is a tool that provides caption- and audio-description services. Runs on Windows 9x/NT/2000/XP/Vista/Windows 7.
Cost: Free