Anime Fillers

A website which shows you which episodes of which animes are fillers and which ones are not
http://www.animefillerlist.com/

Example Naruto Shippuden:
http://www.animefillerlist.com/shows/naruto-shippuden

Another site:
http://www.fillerguide.com/episode-list/naruto-shippuden/1-50