In the very south of Tanaris, is a 'hidden' beach which is part of the treasure map quest. From here you can get to the outer map of Un'Goro, then Silithus and fish in the water surrounding it by running West. You'll have to hearth when you want to leave, unless you want to run all the way back along the outer map, ten through Tanaris again.
Also, follow the River north of Tarren Mill through Alterac to the Plaguelands and try your luck there. You shouldn't encounter any mobs there.
Edited, Jul 27th 2006 at 7:16am EDT by Torux