After you get the "Stone Hammer" at drydry ruins go back to Toad Town and go in a pipe by the sighn that says "PRIVATE" and to the left there is a stone block whick you can now smash. Then you will fight a Blooper. After you defeat the Blooper, three pipes should pop out of the ground. The one to the right takes you to goomba village. The one in the middle takes you to koopa village, and the one to the left takes you to drydry ruins. Now you can warp through towns easily.