Many web-browsers, including Firefox and IE, pop up a list of websites you have previously visited when you enter characters into the address field.a http://www.amazon.co.uk/
Enter the letters of the alphabet individually in order (ie. a, (delete), b, (delete), etc.) and post the top site for each letter. If the site is not worksafe or otherwise inappropriate, you may enter 'inappropriate' or similar text by the letter. If there are no entries, state that. Give your friends an insight into your browsing habits.
Of course, whether it shows recently-visited sites or frequently-visited sites is up to your browser - if you know or can work out this information, you can include it or not, as you will. Ditto for any other comments on your list.
d http://www.dcr.org.uk/ [which I typed in the address bar by mistake yesterday]
e http://www.environment-agency.gov.uk/netregs/processes/ [which doesn't even work — I was trying to find some more info by cutting the end off a valid URL]
g http://www.google.co.uk/ — of course!
v http://www.vibelet.com/ [uk.misc made me do it, honest]
x Search Google for "x"
y Search Google for "y"
I'm pretty sure these are recently visited rather than frequently visited — some of the above I've only ever been to once. Also, it looks like it gives preference to addresses that you typed in favour of those that you merely clicked on ("it" in this case being Mozilla).