Over two million registered Flickr users and counting have discovered the ease and fun of organizing their photo libraries, showing off their favorite pictures to the world, and securely sharing their private pictures with friends, family, or ad hoc groups. But Flickr's own plethora of intuitive menus, options, and features just scratches the surface.

Flickr Hacks goes beyond the basics of storing, sorting, and sharing your photos to the much bigger playground of what's possible. Whether you're a beginner looking to manage your metadata and play with tags, or a programmer in need of a detailed reference of Flickr API methods, you'll find what you're looking for here. In addition to getting under the hood of some of the most popular third-party Flickr toys already in the wild, you'll learn how to:

• Post photos to your blog directly from your cameraphone

• Mash up your own photos or others' public pictures into custom mosaics, collages, sliding puzzles, slideshows, or ransom notes

• Back up your Flickr library to your desktop, and save the comments too

• Set random desktop backgrounds and build your own Flickr screensaver

• Geotag your photos and map your contacts

• Download a list of photos and make a contact sheet

• Make your own Flickr-style tag cloud to visualize the frequency of common tags

• Build a color picker with a dynamic color wheel of Flickr photos

• Feed photos to your web site and subscribe to custom Flickr feeds using RSS

• Talk to the Flickr API using your web browser, Perl, or PHP; authenticate yourself and other users; and build custom API applications