Alright, with the new addition of repl.run, we have lots of great stuff you you! In addition to the repls in this list, the announcement of repl.run included some awesome repls that I suggest you check out!
@leon332157 and @mat1 This may not be a repl, however I feel it deserved a shout out. Right now, repl.it can only be run in your browser. However, through the power of Electron, these people made an unofficial web app!