Flickr is my favorite online source of images: it stores an incredible number of creative and unique photos you can use for inspiration.
Flickr advanced search allows for multiple search options: you can choose to search by tags or full text, media type (photos or videos or both); date, creative commons, etc.
The choice is really great but somehow using the built-in search platform is by far less exciting than taking advantage of numerous external tools that search Flickr creatively.
Search by color:
[NO LONGER WORKS] Flickr Color Selectr allows you to set color preferences by color picker or color properties.
Multicolr allows to mix up to 10 colors and selects images matching the chosen color palette.
Retrievr claims to search images by your "sketches" but all I managed to achieve was to find images by color:
Search by theme:
Tiltomo is an awesome "Flickr Playground" tool that lets you search by tag, color / texture and theme / subject. The service uses two test image databases, works fast and can be real fun to use.
Here is what the tool shows for theme based search for this image:
Search by tags:
PIMPAMPUM searches Flickr photos by tag and has a very easy-to-use flash-based interface: it will display photos in a string and show you the larger version once you click on it:
Findr performs image search by tag and also gives you the huge list of related tags to refine your search.
PiciShare is a Flickr search engine that lets you search by tags or full text; you can also limit the number of images per page and sort the results by relevance, date added or popularity.
Airtightinteractive.com tool displays the images based on your tag choice and also suggests more related tags:
Search by Creative Commons:
Compfight: besides tag-based search, the service lets you set the Creative Commons ('Off', 'Commercial', 'All'), Safe Search and "original photo" filters.
FlickrStorm allows to search by keyword and /or by Creative Commons. The tool also has a handy flash-based interface:
Search by username:
Interestingby.isaias.com.mx rates any username's photos (I wasn't able to define the popularity criteria though).
Search by location:
Flyr [Broken URL Removed] searches within geotagged photos and adds Google map link to each search result.
Geosnapper searches for US cities or zip codes and shows the place instantly on the map:
See random cool photos:
Photoree let's you rate Flickr photos (for registered users) or just browse most popular photos chosen by other members.
Flickriver shows you most interesting photos added today / yesterday (the tool also lets you search by tags, username or group).
Girls on Flickr: shows you most popular girls' photos sorted into the following categories:
pretty, beautiful, portrait, blonde, teens, black-white, sketch, hair, eyes, lips, hands, tattoos, glasses, skirts, shirts, jeans, shoes, uniform, celebrity, actress, model, super model, sports, fashion, cars, laptops, secondlife, interesting.
Which tools do you use to search Flickr? Are there any I missed out?