http://www.svp-team.com/
Stuff like The Hobbit plays at 48fps and some sports broadcasts are 60fps. Well with SVP, you can basically convert any 24/30 fps video to a smooth 60fps movie (or 120fps if have a 120mhz monitor). Works with youtube as well if you know how to stream to an external player or download the video file.SVP allows you to watch any video on your PC file with frame interpolation (like you can watch it on high-end TVs and projectors). It increases frame rate by generating intermediate animation frames between existing ones to produce very smooth, fluid and clear motion. The technology is well-known for a while ("TrimensionDNM", "Motion Plus", "Motionflow" and others), but now it's available for free to PC users with simple GUI and just a couple of mouse clicks.
Some downsides to SVP is that it can cause artifacts on high movement scenes. It also requires decent hardware for smooth playback (CPU and GPU). But I think it's all worth it for the silky smoothiness. Some might say it gives a "soap opera" effect and that its a bad thing, but that's a matter of opinion.
What you need to get it to work:
1. SmoothVideo Project software.
2. FFDShow, the audio/video decoding from this is not required.
3. AviSynth
4. MPC-HC or its derivatives (MPC-BE, PotPlayer, KMplayer, Light-Alloy).
5. Add 'FFDshow raw video filter' to external filters list and set to 'prefer'
6. SVP is running and you can see tray icon.
7. Play video.
*VLC will not work. Same with any MPlayer frontend. You need a player that can use directshow filters.
SVP comes in Full and lite packages. Full has everything you need plus some extras like madvr and reclock. Lite only has SVP but the third party stuff are provided as separate downloads.