One of the nicest browser add-ons I’ve come across for watching photos from flickr, among other photo web sites, or YouTube videos  has to be CoolIris (formerly PicLens).

The add-on inserts a button in your browser’s toolbar that enables you to launch a full screen view of photos or videos you are currently watching from a supported web site.

The application namely includes searching capabilities from web sites such as flickr and YouTube and a slide show view. My only critic is the globe icon, which, instead of downloading a photo or video to your hard disk, opens up a seperate web page with the selected photo. Other than that, it’s really kinda neat!