Open the image you want to manipulate in Photoshop, and then press "Ctrl-J" to duplicate the layer. Press "Shift-Ctrl-N" to open the New Layer window, type "Sunshine Rays" in the name input box ...

Digital Anarchy's Knoll Light Factory 3.0 is the perfect tool for creating realistic - or not, if you so choose - lens flares inside Photoshop.