Flickr

Flickr now hosts more than 4 billion images from users across the globe and its emphasis is on sharing and collecting images uploaded by users. It does include some social functionality, allowing for groups where multiple users can upload photos, comment on them, and share, making it very useful for collecting images of community events or projects.  

Flickr asks photo submitters to organize images using tags, which enable searchers to find images related to particular topics, such as place names or subject matter. Flickr was also an early website to implement tag clouds, which provide access to images tagged with the most popular keywords.

Flickr has also recently added a map feature that allows users to tag their photos and videos to specific geographic locations to show where they were taken. This enables, for example, community members to create profiles of towns, projects or other special places and make them accessible to the entire community.

Finally, Flickr's Creative Commons section is useful for people searching for images to use on websites and in publications without paying royalties. Group pages and collections on themes related to planning may not be available to use, but are also useful for finding examples of community design elements or projects.

Base memberships are free on Flickr, with advanced memberships (useful for hosting large volumes of photos) starting at less than $2/month.