It just so happened that I’ve been asked where Firefox Bookmarks are stored a number of times [more](and I have to admit I also had to look for it the first time) so I figured I’d post here for everyone’s convenience (did the gooling for you)
It’s usually (by deafult I believe) located at C:Documents and Settings
Also, I bring along a cheap 2.5" external drive with me for files et al so I thought hey maybe I should save my bookmarks in there too so I have access to them on machines I use (eg. home and office). For this I would redirect you to this post by Chris Ilias on customizing firefox bookmarks location.
I know I know there are a number of ways of storing bookmarks online but I think the benefit I’m after is if I have firefox bookmarks itself (rather than online bookmarks like del.i.cious or google bookmarks - yes there is such a thing), I can use my AutoComplete Manager add-in. Which is typing in the address bar, the addin doesn’t simply provide suggestions based on words in the URL or bookmark name or page title but all of them plus a couple more options on how you want autocomplete to behave. I’ve been using it for sometime and working good (not to mention some updates/enhancements here and there). This has been in my FF addin list for sometime along with NoScript and a few others.