Drag these bookmarks to your bookmarks toolbar. Clicking on them directly will most likely result only in cryptic error messages.

[2018 update: These were written in 2009 or earlier. Amazingly, they still work after a few tweaks to account for HTTPS URLs. Some will fail on pages with content-security-policy headers that have the effect of blocking bookmarklets.]

• Flickr image -> photo zoom page: When viewing a Flickr image directly (one of those farm1.static.flickr.com links), this will take you to the zoom view, where you can see different photo sizes or go to the comments page. (Test it here.)
• Google cache: View Google's cached copy of the current page.
• Wayback archive: View past versions of the current page, courtesy of the Wayback Machine.