Picasa is an image organizing & photo sharing website. It allows you to organize, edit and share photos online. You can download an individual photo, video, an entire folder from Picasa to computer. To do this, you need to download 'Picasa Desktop Application' on your computer. Picasa allows you to view and edit RAW files. You can save the edited RAW file without any changes to the original RAW file. If you are looking for a step by step process to download RAW files from Picasa.
You can install PicBackMan's Picasa uploader for Mac from the website and start backing up photos and videos.