What/When: , Saturday, 10 a.m. to 3 p.m.
Why go: Save a life! Call 1-866-256-6371 or visit www.inova.org/donateblood to make an appointment. Walk-ins are welcome, but appointments are give priority. Must weigh at least 110 pounds and have a photo ID.
Why go: Shop used books, magazines and audiovisual materials from the Prince William County public library system.
What/When: Auditions for Pied Piper Theatre's production of "The Little Mermaid," Saturday
Where: The Candy Factory, 9419 Battle St.
Why go: The Pied Piper Theatre stages three musical productions for ages 8 through 18 annually. Callbacks are held on Sunday.
Pricing: Auditions are $10; if cast in the play there is a $200 participation fee.
What/When: Book talk, Sunday at 2 p.m.
Where: Manassas Museum
Why go: Talk centers on "the post-war relationship between John Singleton Mosby and Ulysses S. Grant."