For examples in popular music, see the section on “ Tonicization” on Other Modulations here.
Paula Maust, Expanding the Music Theory Canon: Modulation
Diverse Music Theory Examples: Tonicization, Pivot Chord and Direct Modulation, Common-tone Modulation, Abrupt and Enharmonic Modulations
Music By Women: Explore the Database (Click on the Harmonic Progression Filter on the left and select Modulation.)
Yale Musical Examples Database: See the "Harmonic/Scale" tab at the bottom. (Scrool to the bottom for examples of direct modulation in pop)