One of the most popular photo-sharing sites, Flickr is also a great tool for musicians. Besides of course posting your pictures, Flickr is a wonderful tool to build community and communicate with fans, but also find new fans – you can search and make friends, create groups and join groups, all through posting pictures.
A few tips: obviously, post pictures of your shows. But do not limit yourself to that – post pictures of rehearsals, of fans at your shows, of your hometown, of things you like or think are beautiful – all this creates new ways for people to relate to you, and it builds community and makes people feel involved.
This is an excellent article about the use of Flickr for musicians by the always-amazing Ariel Hyatt: check it out, you will not regret it!