Opera has these features built-in. You can sort bookmarks in many ways, and even filter the view, so only ones beginning with certain letters are shown.
Another reason to switch from IE is to use keywords for your bookmarks. So typing 'WebmasterWorld' in my address bar takes me to this forum. '*' takes me to Asterisk*. It's much faster than using the bookmark menus.
Other browsers also allow groups of bookmarks to be saved, so several sites can be opened at once.
I really like the way Opera also allows you to recover from a crash. You can choose to open all the pages you were last looking at. I'm surprised this feature hasn't been adopted by other browsers. (It would be very easy to implement, even I can figure out a simple way to do it.)