Marklets.com is a large searchable database of bookmarklets. What makes it really useful is that it has its own Marklets.com bookmarklet that enables you to search for and run bookmarklets on the fly in your browser — very handy if you just want a bookmarklet for a specific task. I made a screencast to show you how both Marklets.com and its bookmarklet work:
What’s your favorite bookmarklet?
Related GigaOM Pro content (sub. req.): What Does the Future Hold For Browsers?