In the recent school supplies sales at Wal-Mart we found this "Beginning Fractions" dry-erase book with a container full of plastic disks divided into different fractions.
I didn't know for sure if it was age appropriate, but after following the simple instructions on the first few pages Danya seemed to grasp the idea of fractions quickly. She liked making the fractions with the plastic pieces and then writing with the dry erase pen. When I had to stop to feed Kevin, she asked Daniel to do more with her so that she could keep going!
I can't find these online, but I know Wal-Mart carries them for $4. I think they are a really good tool for teaching the basic concept of fractions and how to add simple fractions. It even touches on equivalent fractions and mixed fractions.