Keyboard shortcut to exit browser address bar
Try F6. It toggles between the address bar and the page for most browsers. If you're using Opera though, try Ctrl-L and Escape. ;-)
EDIT: In Chrome, hit F6 to toggle between the address bar, the bookmark bar, and then the page. If you've got the bookmark bar showing, hit F6 once to go from the page to the address bar, and twice to return to your last textbox in focus.