Maybe you want to give credit where it's due, or just make a note of that one awesome site that seems to point you toward all the answers to your tech questions. Searching your browser history can be hit or miss, especially if you want to know how you came to find any particular page. Firefox users have an easy way to keep track of browsing history in threads, like email conversations. Here's how to get started:
First, head over to Mozilla and install the FromWhereToWhere add-on.
The next time you want to head down Memory Lane, instead of hitting Ctrl-H, choose "FromWhereToWhere" in the Tools menu, then select "Search History."
You should see a new tab with your history laid out in easily tracked threads. (Note that FWTW only starts keeping track of your history from the point it was installed, so at first it's a big blank tab.)
The add-on also has a feature accessible from the Tools menu called "Link Suggestion" that delivers similar site links in a pop-up window. I didn't find this feature especially useful, but it might be handy for specialized searches, so you may want to check it out.
Note that this add-on just makes use of Firefox's browsing data, so if you clear your history, you also clear FWTW. Of course, that also means that your privacy is just as safe with the add-on as without it.