I created a set PSD-ready 3-Point Perspective Grids, both Bird's and Worm's Eye, with properly named layers and examples for ease-of-use. The file is 85.75 MB because it is 7000 pixels (for those of you who like to work large). Enjoy! If something is wrong with it, please do not hesitate to let me know.
P.S. Best if used for designing props and vehicles, similar to what Feng Zhu does in this example: http://www.artbyfeng.com/images/gallery_image_381.jpg