Cloudup is one interesting service from Automattic which offers a simple way to capture screenshot with a shortlink. You can also upload images, videos, music, pdfs, etc. and quickly convert it to a shortened url. One nice feature it has is the “oembed” which automatically show a preview of its contents when you paste it with software that supports it like the WordPress editor (see sample below).

https://cloudup.com/cnr6-pXHIlz

Best this is its free for the 1,000 items that you upload so signup now: https://cloudup.com/

Hopefully in the feature they can add an ability to put text comments on top of the uploaded images similar to the screencast software.

(Image credits to site/product owners)