Okay. Google doesn't offer Picasa for the Mac. Why? Because we don't need it! If you purchased your Mac over the last few years or you've purchased the awesome iLife package ($74US Retail), then you already have iPhoto. iPhoto does everything Picasa does and quite a bit more! (Can Picasa work with RAW files?).
This Instructable is the Mac answer to' fabulous, but Windows-centric Quick and Great Photo Editing with Picasa. To be fair, we will just import a picture, straighten it, color correct it, crop it and resize it in under a minute. While there's a great deal we could do more, this just shows the procedure to duplicate on the Mac what was done on a PC with Picasa.
Note: Like all of my Instructables, this one was done entirely using iPhoto, Preview and Mac OS X's built-in screen capturing features. Okay… Some of my Instructables have diagrams that were created in Appleworks or Eagle.