http://top100tubes.com/
1 XHamster.com 43 43 (+1)
2 XVideos.com 50 51 (+1)
3 PornHub.com 68 68 (+1)
4 RedTube.com 81 84 (+1)
5 Youporn.com 101 103 (+1)
6 xnxx.com 112 113 (+1)
7 Tube8.com 134 135 (+1)
8 youjizz.com 236 236 (+1)
9 hardsextube.com 267 273 (+1)
but maybe not accurate at all