New bookmarklet: counters
(drag to Links-bar or right-click to Add to Favorites)

Tested in IE6 and Firefox. For every mouseclick, a small [1], [2], [3] incrementing counter will appear. Handy if you want to easily count the number of times something occurs on a page, such as the number of films you've seen of a specific IMDb actor/director (which prompted this idea in my case).