Maybe I'm a little late to the game on this one, but I found these adorable cotton onesies from HuddyBuddy.com to be simple and fun. I love the "I take my milk fresh from the source" chatterbox onesie, and apparently when J-Lo had her twins, Marc Anthony picked up the twin set onesies from Huddy Buddy too.
The single chatterbox tee is $22 and the twin set is $40. I'm all about supporting moms who are passionate about their kids and creative enough to start a successful business from home. You can check out all of Huddy Buddy's collection of tees and onesies at www.huddybuddy.com