Backpack is the third application from 37signals that’s now available online. Just like Basecamp came birth to Rails itself, Ta-da drove great features like caching, Backpack has been the main driver for a lot of interesting developments in Rails. Most visibly is the incredibly strong support for Ajax interfaces that Rails now sports.

The innerHTML approach with server-side fragment rendering was developed specifically for Backpack and has now been extracted for general use in Rails. It’s joyful to see that the Ajax integration in Rails has caught the interest of so many developers and 37signals is especially thankful for the work of people like Sam Stephenson, Thomas Fuchs, Sean Treadway, and others.

Over the coming weeks, we’ll be taking advantage of even more of the Ajax innovation happening in Rails, such as the upload progress indicator and the Google Suggest-style searching. In the meanwhile, do checkout Backpack as the currently best example of the wonders of Ajax in Rails.