I adore the upcoming baseball shirt trend. So casual, so boyish and yet so cute! I found some on ebay, here with a lot of colour choices, but you can also get them cheap or 2-4-1 in JayJays and Factorie clothing (or so my male sources say)
I'm still waiting to see whether or not one's made for men will have the desired fit but I'm planning some outfits around acid wash denim and tight pants nonetheless.
p.s. If men's clothing isn't your thing American Apparel and Asos sell some great womens ones.