For being just a simple screenshot-sharing utility, GrabBox is pretty versatile and feature-rich:
- Free hosting (via Dropbox) with no ads.
- Automatic short URLs, for convenient tweeting (optional).
- Full control over which screenshots get uploaded.
- Ability to specify a screenshot file-name or to let GrabBox generate one automatically.
- Choose between a Dock icon or a discreet menubar item.
GrabBox is a completely free and available right now.