Skitch is an application for OSX which can take screenshots, add annotations, and share the images to multiple destinations such as Evernote, FTP, or a WebDAV endpoint.
After being acquired by Evernote, Skitch 2.0 removed the ability to share to WebDAV endpoints.
You can still download the last version of Skitch 1.0 from Evernote here: http://get.skitch.com/Skitch-1.0.12.zip
Use with IndieWeb Sites
Because Skitch supports sending files to a WebDAV endpoint, it is possible to use Skitch to post screenshots to one's own website, assuming the website supports WebDAV.