TeenyGrab is a free alternative to TinyGrab. TinyGrab is a popular application for quickly uploading screenshots, and sharing them. The only problem is, the full version (with features such as uploading to a custom FTP server) costs $$$. While I have nothing against making a paycheck, it seems like software with such simple functionality should be free.
That's what TeenyGrab is.
You can save the screenshots to disk, copy them to your clipboard, or upload them to FTP or Imgur.com all with the touch of a button.