You can adjust Picasa settings to control which file types are displayed in your Picasa Library. Picasa for Windows supports the following file types:
Photos: .jpeg, .tif, .tiff, .bmp, .gif, .psd (Photoshop), .png, .tga, and selected RAW formats.
Videos: For general playback in Picasa: .mpg, .mod, .mmv, .tod, .wmv, .asf, .avi, .divx, .mov, .m4v, .3gp, .3g2, .mp4, .m2t, .m2ts, .mts, .mkv. For several of these file types, the correct software is required for playback.
For use in Movie Maker: .avi, .asf, .wmv, .mpg, .m2t, .mmv, .m2ts
Audio: (for slideshows and the Movie Maker): .wma and .mp3
You can install PicBackMan's Picasa uploader for Mac from the website and start backing up photos and videos.