Flickr, a popular photo-sharing and -hosting service owned by Yahoo, is to photos what YouTube is to video: it is the quintessential picture site. The service provides a virtual gallery (or many virtual galleries, if you prefer) where people share and explore each other's photos, and the result is an active and engaged community with a vested interest in digital photography.
Flickr offers a plethora of features, which vary depending on whether you subscribe to the free service or the pro version, which runs $24.95. Basic users can share and host hundreds of their own pictures on Flickr without paying a dime, although storage is somewhat limited (the allowance is 100MB). Those who elect to pay for the pro service can enjoy unlimited sharing and storage. In addition, Flickr supports HD video. Unlike other sharing sites though, users videos are capped to about a minute, which the creators hope will create a whole new genre of videography that's a little more like a long-form photo.
Both photos and videos can be accessed in Flickr's API, which has led to some interesting third-party mash-ups. It's also made for some neat ways to integrate Flickr shots into blogs and social-networking profiles. The service's interface hasn't changed dramatically over the years, retaining a clean and simplistic look with a white background that forces full attention on the photography. In order to utilize the service for more than just browsing, a Yahoo ID is required, which may be a turn-off for some users.