My problem is well-known. Like anyone else who spends a generous chunk of time following hyperlinks across the Web, I have a long yet ever-growing list of bookmarks in Firefox. To make sense out of the list, I keep the bookmarks in a menagerie of folders and folders-within-folders. It's easier to find a bookmark this way, but now I must potentially go through multiple folder levels before arriving at the actual bookmark. Moreover, I regularly visit only a handful or two of the bookmarks. I want to keep my organization scheme but also keep bookmark access convenient, especially for the most-visited bookmarks.
There's some great options available. The bookmark sidebar, opened and closed with Ctrl-B, has a search input that searches as you type. Any bookmark has an assignable Keyword property that will take you to that bookmark when you enter it into the address field. Either technique works well if you know exactly what bookmark you want to access. What I wanted was a way to group all of my most-visited sites in one folder, preferably automatically, then just use that folder for my common browsing. Desktops already provide something like this in startup menus for frequently-used programs. Interestingly, the general idea of "virtual bookmark folders" was in the planning for Firefox 2, but postponed. A way to accomplish this in the mean time, as well as affording ultimate (manual) control, would be to open up all of your commonly visited sites in a set of tabs, then Bookmark All Tabs.
OK, next I turned to the legion Firefox extensions. I tried Sort Bookmarks first. It lived up to its name. I'll keep this extension around. I liked that the bookmarks I cared for most were now at the top of each folder's list, but the problem of too many folders was still present. I started to go through the code for this extension to gauge how I could create my own extension for an automatically-updating "Frequently Visited Bookmarks" folder. Then I found the Autocomplete Manager extension. With this, bookmarks can appear in the address field's autocomplete list matching against the bookmark URL or title, and the bookmarks can be sorted most often visited first. Sure, it's not the most efficient search in the world, but it beats having to pop open the bookmarks sidebar or enter and memorize bookmark keywords. My remaining concern is that Firefox seems to have trouble sometimes keeping track of when I visit a particular address, resulting in low visit counts.
EDIT: It seems that restarting Firefox somehow updates the visit counts. I'd say to go figure, but I'm not going to; why should you? I have kept Firefox open for more than a week at a time, but starting it anew each day isn't that burdensome, I suppose.