Instagram is one of those early adopter favorites that quickly crossed the chasm to more mainstream users, at least within my social network. Take that popularity, mix it with an apparent desire to buy shirts, and it was inevitable that someone would use the Instagram API to create wearable mashups. In fact, there are at least three such services, each with its own twist.
So, you're trying to share some files with someone who only has access to an old version of Word. Or maybe that Microsoft-hating friend of yours who only uses WordPerfect. Perhaps you want that old-school ebook to be an epub, rather than .lit. For any of these problems, there are desktop apps that work, of course. However, sometimes you want to be able to do that within a program. If so, Doxument and the beautiful Doxument API are what you need.
As announced on the Flickr Blog, Flickr has launched a new website for developers: Flickr Code. And besides announcing the new site they've both a) given interesting details on just how much API traffic they do each day (see below), and b) they announced they're open sourcing Flickr Uploadr, the cross-platform (Windows and OS X) desktop tool for uploading photos to Flickr.