From the top of my head I can think of -
- Jin, Sawyer and Michael return from their journey across the island with the Tailies in "Collision"
- Kate and Sawyer return after escaping from the Others in "Tricia Tanaka is Dead"
- Jack returns to the camp with Juliet, Sayid and Kate in "One of Us"
- Jack and Hurley is greeted by Sun in "Dr. Linus"