Tantive IV, Utapau, Polis Massa, Dagobah, and Mygeeto.
While Luke flies his fighter to Dagobah to find legendary Jedi Master Yoda, Han and Leia escape in the Millenium Falcon to Cloud City, where Lando (Billy Dee Williams), a smuggler friend of Han rules a community of smugglers.
In the first three movies (Chapters four-six), the pair are often parted, as Luke needs Artoo to help him maintain his fighter when he goes to Dagobah, and Threepio hangs with Han and Leia as they run the Rebel Alliance in Luke's absence.