The World Expo 2010 being held in Shanghai is comprised of 5 "zones" (A, B, C, D, and E). There are, of course, various busses that will take you to the Expo entrance. In addition, you can take the subway (Line 13) to enter. There are only three stops on line 13: The entrance is on Madang Road, where you will go through security and they will check your Expo ticket. The first stop is just outside Zone D of the West Puxi side of the Expo. The second stop is within Zone B of the East Pudong side of the Expo.
Map retrieved from official World Expo 2010 website
Located on the East (Pudong) side are Zones A, B, and C. Here, you can find the Expo Boulevard, World Expo Center, Expo Performance Center, various Theme Pavilions, International Organization Pavilions, and all the National Pavilions. There are five entrances here and three ferry docks where you can cross the river to the other zones.
ZONE A: Asia and Middle East National Pavilions
ZONE B: Southeast Asia and Oceania National Pavilions, and other structures and pavilions
ZONE C: Europe, Americas, and Africa National Pavilions
Located on the West (Puxi) side are Zones D and E. Here, you can find the various Corporate Pavilions and most of the Theme Pavilions. There are three entrances here and three ferry docks to cross the river to the other zones.
ZONE D: Corporate Pavilions are located here
ZONE E: Some Corporate Pavilions and Theme Pavilions are located here.