PictureSandbox
Picturesandbox.com uses the Flickr search APIs to return images by all users on Flickr.

Preloadr
Preloadr offers free photo editing for Flickr. Simply log in to Flickr and authorize Preloadr to access your photostream you can then choose images to crop, flip or rotate.

PlantWire
PlantWire uses publicly licensed Flickr photos to identify flowers and plants. Currently, their floral database contains over 300 plants and over 6000 images.

Phlogre
Photo Organizer for local photos and flickr photos. Meant to replace the official Flickr Uploadr.

PicMarkr Pro – $21.99
Watermark images, protect your pictures copyright,
import and backup Flickr images to your computer
with PicMarkr Pro

PicMarkr
Add custom watermark (image or text) to your images online and free.

Pictobrowser
A widget to display flickr photos on your blog.

Phlickr
An open source PHP5 based api kit used to access the Flickr API.

Photo Comment Tool
One-click grab and publish any Flickr photo into a Flickr photo comment stream or forum post.

Flickr People Finder
A way of finding people on the big flickr visualization.

Photoupload
Image uploader to flickr. Upload photos directly to photoset, Use IPTC and EXIF fields in photo description, and generate tags from IPTC keywords.

Flickr Postcard Browser
Browse Flickr Postcards