Pixel-Peeper is a service that allows you to pixel-peep (even at 100% of the original size for given camera) at thousands of full-size photos in our database, therefore allowing you to check a lens, digital SLR camera, or a digicam before buying one.
Because all cameras and lenses yield a very different picture quality at different apertures, ISO speeds or focal lengths, all these parameters can be set to help you check a lens or camera at its extremes.
Pixel-Peeper is and always will stay a free service presented by a photographer (here's my flickr page) for the photo community.
I decided to launch Pixel-Peeper because I was in need of such service myself. All the reviews sites on the net are great and provide valuable information but the most objective way to find out which lens to purchase is by checking photos made with such lens. Of course lenses behave differently at different apertures and focal lengths, so this is why you can also use these settings to parameterize the searches on pixel-peeper.com. Often having to spend a $1000 or more on a lens is a good enough reason to do some research first. Another way to use the service is by checking cameras against parameters such as ISO or their built-in lenses (for digicams/compacts). All photos are at least 7MP of size and you can choose to only see full-size images, at camera's max resolution.
All the functionality is provided thanks to the innovative approach to photo sharing presented by flickr. If you don't have an account yet, I'd strongly suggest you sign up. It's free and you will certainly get hooked!
The pixel-peeping pleasure awaits you!