It's a holiday weekend, so the stars are out. In this case, that means Julia Roberts and Tom Hanks in one corner, and Optimus Prime and Megatron in the other. They'll battle it out this weekend at the box office, as Larry Crowne and Transformers: Dark of the Moon open in wide release.

The only other film opening widely this weekend is Monte Carlo, a romantic comedy in which Selena Gomez, Leighton Meester, and Katie Cassidy play three friends posing as wealthy socialites in Monaco.

Among the movies opening in limited release are The Perfect Host, a thriller starring David Hyde Pierce and Clayne Crawford, in which a fugitive gets more than he bargained for when he crashes a dinner party; and Terri, a comedy drama about a teen misfit and the assistant school principal (John C. Reilly) who takes an interest in him.

As always, check out Adweek's mashup of all the opening-movie trailers, above.