update Sept 2015: nice explanation of how geojson-vt works here

Mapbox technologies used in their webgl and opengl libraries are being extracted into standalone pieces. Vladimir Agafonkin,creator of leaflet.js, earcut.js provided slicing and polygon simplification library for geojson called Goejson-vt.Geojson-vt can slice geosjon into tiles aka mapbox tiles.
Quick test and sample of using geojson-vt on leaflet with canvas drawing available here: http://bl.ocks.org/sumbera/c67e5551b21c68dc8299

2 videos:

Overview of various geojson samples

folowing video shows 280 MB large geojson !

for comparison here is WebGL version on the same data. This version is loading all data into GPU and leaves everything on WebGL (no optimization). It also takes slightly more time to tessellate all polygons, but once done all seems to run fine. Code used is available here