Power-drag is simply cool. Probably I should call it "awesome script"? Pressing your shift key then hover textareas, select boxes, iframes, objects, images or input fields to simply resize them by dragging its lower right corner. Simple, clean and efficient. Double click to restore the original dimensions. You can enable the dragging corner always, or use another modifier key. The script requires shift by default because makes the script less intrusive, and does not cover small elements in the page, while having a smaller performance impact.
Offers single-key and modifier key shortcuts to most functions related to browsing and developing websites.
This isn't mine, it's a part of Moose's Designer toolset. This is based on the version from 2007/07/11. I didn't keep the original file (I thought I could always grab it from his website again), but the changes are minor. I added Ctrl + 4 to allow exiting without having to deselect textareas first, for instance. An alternative approach (i.e. the only one endorsed by Moose) is Esc, 4.