If you are looking for cool world cup t-shirts, look no further than Didi. They have t-shirts for most of the major teams. My particular favourite is this USA one, listing all top players as well as the hapless England goal keeper, Robert Green, who fumbled the ball allowing USA to draw 1-1 earlier in the month.
[28/6] Right now it seems like all the shirts are sold out but hopefully they will reprint some more.