We are all familiar with URLs: the string uniquely identifying the requested document. However, we don’t always consider they are more than that: URLs are user facing and should be considered important UI elements.
— Andreas Bonini
It’s worth considering that URL design is a part of user experience not just a programming concern.
There’s a growing number of social networks and sharing sites geared towards designers and front-end developers.
There’s some established networks in this list along with some of the up and coming networks you might not have thought of yet. This list is by no means exhaustive. Want to add a network? Please add it to the list or in the comments along with why you find it valuable!