Up to and including Firefox 3 I could press Ctrl+E to switch focus to the search text box - old habits hard to change, I'd rather not adapt to Ctrl+K for this. Is there a way I can change the shortcut back to Ctrl+E?
I think you want keyconfig. There appears to be a version available for FF5: http://mozilla.dorando.at/readme.html
More info here: http://forums.mozillazine.org/viewtopic.php?t=72994
XPI here: http://mozilla.dorando.at/keyconfig.xpi
Fair warning, I haven't tried to get keyconfig working in FF5. But I have used a version of keyconfig with older versions of FF as well as with Thunderbird and it does what you want: lets you remap key configurations to suit your preferences.