Here's a fun little quiz I found via kottke for people here. I missed 67 countries, but I found the time pressure kind of neat. I was working my way west to east across the world and found myself still typing in long African country names with only two minutes left, and not having started Asia or Oceania, so definitely more time would have helped. A tip for slow typers (or anyone who knows enough countries to have time pressure in 10 minutes) - stick to one word countries. I also tripped myself up by typing in "Bahamas" instead of "The Bahamas" several times, and misspelling Libya "Lybia" or "Libia" at least three or four times in an attempt to get that country at the top of Africa that I knew should be in there.
http://andys.org.uk/countryquiz/