A great collection of online plays. Many also have access to monologue searching.
Most of our books of monologues have call numbers beginning with PN 2080 and are shelved on the 8th floor. In BobCat There is no specific subject heading for scene books. you can perform a keyword search in the catalog for the term monologues. I'd recommend using the Play Index. It will restrict the play by gender, and number of people in the cast.