I recycled some tshirts into a valentine's top for my daughter. I used a tutorial I found online for the heart.
I should not have tried to reuse the neckline from the tshirt. It was rather stretched out. I will have to remove it.

This is Otto 6/2010 #19 in size 110. My dd is 4 and wears rtw size 5. It fits her really well. I will have to rip off the neck and redo it. It has gathering on the sides.
The heart is made by sewing little "noodle" pieces of knit into the heart shape and then trimming them neatly.