Adding to zro's link, I added a post over there, but in case you miss it, I just wanted to add it here as well:
This is just a little shortcut/trick I stumbled across and use all the time now.
once you have the bookmark in your bookmarks... if you then drag it to your bookmarks bar to the beginning of your list of bookmarks, you can now use a builtin shortcut.
The first bookmark in your bookmark bar (that isn't a folder) is OPTION + 1, the second OPTION+2.. and so on. I use that to get back to my home page (iGoogle) and for TinyURL, two sites I use frequently each hour.