After a too-long hiatus, I have recently been rediscovering Flickr. Flickr is an online community-plus-tools web site, but the focus is on visual arts and sharing images-- so the community, by default, it set up to truly speak our language. I believe Flickr started as a site used primarily by photographers. But by the time I first purchased a "Pro" account there years ago ($25 a year and totally worth it), it already had gained a very solid reputation as a de facto clubhouse for illustrators, too.
For illustrators, Flickr is a great option if you wish to show off some of your art that may not be appropriate for your main portfolio, but still deserves an audience. Do you have work hiding that still is valid, quality work that helps to tell your story and show your range? If it doesn't fit into your professional web site portfolio stylistically or thematically, Flickr could be just the place to show this art off. It has a sort-of casual, more experimental vibe, and the audience is usually made up of supportive peers and fans of illustration.
For illustrators, Flickr is also a great place to do reference research. You will find a group posting photos on specific subject matter for just about any topic you can think of. I'm a member of groups which feature vintage children's books, advertisements from the 50's, and old halloween-themed art, goods and ads. I have even started a couple of groups myself. At one point, I wanted to post some coastal art, and oddly there was no suitable existing group. I started one, and others have since joined and post to it as well. It's fun! "If you build it, they will come" is not always true in the physical world, but in the Land of Flickr, it's very likely!
The community and social networking aspect of Flickr is one of the things that makes it extra special and this is one of the most important aspects of Flickr. It is a great place to build your online social network. You canmake other users a Contact. You can comment on any image or mark it a Favorite, telling everyone that you like it. These, along with other little tools of self-expression can easily lead to dialogue and meeting others with similar interests and goals. It's fun and gratifying to connect with others through art appreciation. On Flickr this happens in a very natural, unforced way because everyone else is also there for the love of visual arts and photography and also for their own personal obsession (see Groups, above!). How nice and comfortable it is that this is where the focus stays on Flickr: peoole are, by and large, there for "the love of the game".
Flickr is a very comfortable place to accomplish a lot online. If you want a lot of "Bang for your Buck" in terms of social networking, beautiful portfolio viewing with ease, plus an indispensable reference tool, Flickr is the way to go.