PhET Simulation: Photoelectric Effect
This sim provides a robust set of tools for teachers to customize the modeling experience from conceptual physics through AP.  Students can switch among five different metals, control wavelength, light intensity, and voltage to recreate the experiment that spawned the field of quantum mechanics. For lesson plans that specifically support this simulation, see the recommendations directly below.
Photoelectric Effect Conceptual Exploration: PhET Teacher Contribution -- Conceptual Physics
This lesson by high school teacher Kelly Warner is appropriate for a conceptual physics course or a combined introductory physics/chemistry survey course. It provides explicit guidelines for students to use the Photoelectric Effect simulation to predict what will happen to a metal surface when light of different wavelengths strikes it, what factors affect electron ejection, and how the model can help them understand which metals would be most/least reactive. Little mathematics is introduced in this lesson. NOTE: Only registered users can access teacher-created materials on PhET, but registration is quick and easy.
Photoelectric Effect-Graph Exploration: PhET Teacher Contribution -- Algebra-Based Physics
This question set by Colorado high school teacher Kristy Bibbey is a standout because it has a complete answer key plus additional content support for teachers on how to interpret graphs of Energy (in electron volts) vs. Frequency, Current vs. Voltage, and Current vs. Light Intensity. It could be a great jumping-off point for introducing the math of stopping voltage, work function, and threshold frequency. It also serves to provide multiple representations of the conceptual basis for the photoelectric effect, going beyond "plug & chug". Appropriate for an introductory algebra-based or calculus-based physics course. NOTE: Only registered PhET users can access teacher-created materials, but registration is free and easy.
Photoelectric Effect Questions: PhET Teacher Contribution -- Algebra-Based Physics
This guided activity by Australian high school teacher Simon Lees takes the stakes a bit higher by introducing the wave frequency equation and demonstrating how to use Planck's Constant to determine the energy present in a photon. It takes learners step-by-step through a simple way to determine threshold frequency from a graph that is auto-generated in the simulation. It would be appropriate for an Algebra-Based Physics course. NOTE: You must be a registered PhET user to access this Student Guide. Answer key is not provided.
Photoelectric Effect Inquiry Lab: Teacher Contribution -- AP Physics
This Student Guide, designed by HS teacher Jonathan Carlson for the calculus-based or AP physics course, takes students step-by-step through the calculations associated with the photoelectric effect. Students will use the PhET Photoelectric Effect simulation to calculate stopping voltage, kinetic energy of a photon in Joules, and learn how to determine threshold frequency and work function from graphical data. This resource contains an answer key. NOTE: Access to this resource is available only to registered PhET users, but registration is free and easy.
Photoelectric Effect: Power Point Presentation
This link takes you to a Power Point containing lecture notes and clicker questions developed by the PhET management team for use with the Photoelectric Effect simulation. You can download the entire presentation as a ppt file to quickly embed in your own lesson, or you can open it in a browser tab. NOTE: This resource is available only to registered users of PhET, but registration is free and easy.