Below is a list of applications built using phpFlickr (that I know of). If I've missed a link or if you have built a new app, let me know and I'll add it.
- Admiral photo galleries by Eliot Shepard - An application that builds static pages based on your Flickr photosets. Since it's static, if Flickr goes down, your albums stay active.
- calendarFlickr script by Dan Steingart - Create a calendar for your site that displays thumbnails of a photo that you took on that day.
- Flickr Module for CMS Made Simple by Allan Larsen - This is a module integrated into CMS Made Simple to display your photo albums from Flickr.
- Flickr DHTML Badge by Joe Tan - You know that neat flash badge that Flickr has? Now you can display one on your website made with DHTML. It even includes the cool fading stuff.
- Flyr by Paul Downey - This Flickr/Google Maps application lets you search for the locations of photos by tag, titles, descriptions, and/or Flickr user.
- Multiple tags RSS feeds by Richard Eriksson - This cool little script lets you make custom RSS feeds of Flickr pictures searching by multiple tags.
- Quickr Pickr by Nolan Touchstone - A quicker way to generate HTML code of Flickr pictures for use in Xanga, other blogs, or any HTML Page.
- Tag cloud PHP script by Dan Steingart - Create one of those nifty "tag clouds". I don't know where he heard the quote, "The tag cloud is the mullet of the internet," but I'm onboard.
- FlickrFly by Rob Roy- drop a link into the description or comment of a geotagged Flickr photo, and fly to that place in Google Earth.
- FlickrFeub by fabian. - helps you to retrieve pictures from Flickr in an easier & quicker way than from the actual Flickr interface.
- h4ppierphotos by Christian Seaman - advanced filtering and batch editing made easy.
- flickr4j by Nicolas Born - A really cool plugin to display your Flickr photos in the Joomla CMS.
- Preloadr - Edit your Flickr images from a really cool Javascript interface. This allows more than the usual crop, resize and rotate. Definitely worth checking out.