Most video players support changing the playback speed. In mplayer it's controlled with the '[' and ']' keys and in VLC it's set in the Playback -> Speed menu.
HTML5 video elements also usually have a playback speed property that can be changed in the JS console, so any site that streams fast enough can be sped up.
Note, one can do the same with ffmpeg:
https://ffmpeg.org/ffmpeg-filters.html#setpts_002c-asetpts
http://stackoverflow.com/questions/30371346/whats-right-way-...