The music during the ending credits is a cover of David Bowie's "Life on Mars" by Trent Reznor & Atticus Ross.
A copy of Fogdancing by Max Shea is seen on a movie rack when Angela purchases a copy of Sister Night. The movie (and the book the movie is based on) are fictitious and part of the Watchmen universe.
A cardboard cut-out of Dr. Manahattan is shown when Angela buys her movie. The cut-out is based on the comic book character.
If you look behind Angela when she checks out her grandmother, you can see a picture of Dr. Manhattan with red devil horns and "murderer" written across his belly. While it's weird that it's written in English, it's a great touch considering what he did during the war.