Sparked off by http://meta.gardening.stackexchange.com/questions/251/better-image-embeddeding-and-viewing, http://meta.diy.stackexchange.com/questions/549/change-the-image-upload-so-that-a-thumbnail-is-shown-and-the-full-size-image-lin
Thanks to @yoda for the idea!
When you upload an image using the SE uploading dialog, it gets uploaded in exactly the same size that the file is in. For large images, this can be a problem since they take up a lot of space and screw the alignment. The uploader doesn't allow for resizing (except by manually changing the URL to one ending in s, m, or l.
This script provides an improved upload dialog:
##Installation##
Click here to install. Will only work in Chrome or Firefox (the latter requires Greasemonkey).