Puush is a small and simple application and web service which makes it easy to take and share screen grabs, as well as pictures and other files.
Before you can use the program you must create a puush account. It's nothing that you haven't done many times before with other services, though: give them an email address and password, click a "verify this address" link, choose a user name and you're done.
Launch puush, log in, and you're ready to begin sharing screen captures - which really is very quick and easy. To grab an image of your current window, for instance, you would just press Ctrl+Shift+2 (by default, anyway - all the hotkeys are user-configurable). No dialog appears, no options, there's nothing else to do: but in the background the program is taking the image and uploading it to your account. Within a few seconds an audio alert tells you that's complete, and puush will copy a short URL to your clipboard (of the form http://puu.sh/xxxxx) which you can use immediately to share the picture with others.
If grabbing an individual window doesn't suit your needs, you can also press hotkeys to capture a specific area, the entire desktop or the contents of your clipboard, as well as a specific file (they'll also each be uploaded to your account).
And if you're taking several grabs, then puush conveniently allows you to review some of them directly from its system tray menu. We found the program always listed our last five images and their time of capture; choosing one of these displayed an image thumbnail, and links to open it in our browser, copy its sharing link to the clipboard, or delete the image entirely.
The free edition of puush has one limitation: files will expire after they've not been accessed for 30 days. Paying for a Pro account lifts this to 6 months, and gets you Dropbox sync as well.