For quick-and-dirty screen captures you want to easily share, Snipboard.io’s one heck of a convenient and free go-to tool. No registration needed at all, but it lets you manage and delete any images you’ve captured and posted if you do register. Or you can just keep them up there forever like I do, since it auto-generates a unique URL for each image you post, and folks will need that link to view it.
Great for sharing with, say, tech support, or someone you’re tutoring/giving instructions to, etc. For example, here’s a screenshot of the Wordpreneur Toolbox page I took not that many seconds ago, now available for you (or anyone I give the link to) to view on Snipboard.io.