Trav
Chaos
I find trav to be excellent because you can farm it on P1, which means if you don't have 8 copies of D2, you can just go there without wondering about split game time (I mean, nobody likes a split game that lasts 1 min tops). Which makes it my #1 go-to place for rune farming. It's a static map, gets you a shitload of other stuff in between the highrune drops,
You can't get bored of trav (or at least, I havent yet)