Suggestions for Browser Bookmark Management?

slashdot_commentator asks: "My bookmark collection has hit a few thousand at this point. Anything that looks interesting, or may be of interest in the future, I tuck away. I group them in roughly 30 different subfolders based on topic. I've decided I consume too much effort in organizing them, and need to find a better solution. I've looked at radically different systems like del.icio.us, but its not for me. I'm even toying with writing a plugin/replacement to the current built-in bookmark manager. Can anyone recommend a plugin or package? Or alternately, features they would like to see in a 'bookmark manager'?"