1) Adjust the Smart Location Bar’s Number of Suggestions
In Firefox 3, when you start typing in the location bar, a drop-down list of suggestion URLs will be shown. If you want it to show more than 12 suggestions (12 is the default), you can adjust the browser.urlbar.maxRichResults keys and get it to show the number you want.
Config name: browser.urlbar.maxRichResults
Modified value: Set to your desired number of suggestion. If you want to disable it all together, set it to -1
I just set mine to 5, and I like it much better this way. Changed several other settings too, including "click on URL box puts insert caret where you clicked", which I like a lot better than the default "highlight whole URL" behavior. And I have a feeling that a lot of people will really like the "release memory upon minimize" setting...