Flickr is a great way to share photos. If you become a member, you can upload your photos, organise them into sets, join groups, and so on. You decide whether you want to set the photos to private or share them with others (there are different levels of privacy).

French Circus advertisements 1885-1925 on Flickr by DoubleM2
Index of images from blog 'But does it float?'
Very interesting illustrations from A Journey Round My Skull's sets on Flickr

kraftgenie's photostream on Flickr
kraftgenie's Weimar set on Flickr which accompanies the blog, Weimar

Guggenheim Museum's flickr sets
Flickr Sets by laura@popdesign Laura writes the Animalarium blog.
Flickr origami set2by Eric Gjerde
Flickr origami setby Eric Gjerde
All Eric's origami and tessellation sets are here.See Eric Gjerde's website Origami tessellations
Art21's flickr photostream
Bibimorvarid's Art&Design set
Bibimorvarid's photostream
Papercraft and mail art- by Corduroy Cat
Altered playing cards by Corduroy Cat.
Atcs and inchies by Corduroy Cat.
Corduroy Cat's contacts and groups on Flickr (lots of stuff to explore here)
malen'kaya_lo's photostream
merlinprincesse's photostream
tjenmyt's photostream
Irina Troitskaya's photostream
ma-ruk's photostream
ONE-LIFE-K.N's photostream
Inca Pan's photostream
Inca Pan's illustrations
Inca Pan's paintings
Katarina2353's photostream
Vintage dictionary and encyclopedia pages for collage
Alice in Wonderland and Through the looking glass illustrations
Vintage science illustrations
Mid C20 science illustrations
In Stadten geschehen seltsame Dinge's photostream
artyfishal44's photostream Colourful digital art
Wanda Pietrzak (in transition)'s photostream surrealist photography
Periodic table printmaking project