Tweetshots – turns your Tweet into an embeddable screenshot. Click on the Tweet you want to turn into an image and copy the URL. Open Tweetshots in a different window/tab and then paste the URL in to the box that says “enter a bookmarklet name”. Drag the bookmarklet to your bookmarks/browser bar. Navigate back to your Tweet and click on the bookmarklet. You then get the option to copy the image or code to embed or post directly to your Tumblelog.*
via @twtooltrack
See the comment on this post for better instructions!
Twitter Apps 