While not nearly as cool as the Muxtape playlist viewer we wrote about a few months back, if you're looking to add a little extra eye candy to your bookmarks folder, it's worth checking out an extension called Bookmarks Preview. When installed, it adds two new views to your bookmarks folder that let you surf your bookmarked sites with small thumbnail previews. You can either view them in a large grid, or Apple Cover Flow-style, which will scale up each thumbnail to a maximum of about 440 pixels wide.
Each time you bookmark a new site a thumbnail will be created and stored away. It will also go back into pre-existing bookmarks and grab thumbnails the first time they're added, giving you a rather large library to look at. My collection took about five minutes to get converted and came up about 50 percent blank. There's currently no way to have it go out again and fetch newer, updated versions--something I hope is added in a later version.