Before we go any further I should point out that I love browsing Flickr and have always found Flickr's mobile site to be a bit lacking (that's a nice way of saying it sucks). Exposure lets you do everything you can do on Flickr's website and more. The neatest feature, and the creepiest, is the 'Near Me' button. Press it, and through the magic of Core Location, Exposure will show you all the photos on Flickr that were taken near your current location.
Check out the gallery for a full tour of this great iPhone app.
Exposure comes in a free ad supported version, and a premium version sans ads is available for $9.99.