My best find was probably these free printable Angry Birds characters from The Party Animal-- I used them to create Angry Bird balloon characters which I hung from my curtain rod, as well as for the colored paper gift bags. Such an awesome find, and these really helped bring the theme to life.
The cake was another awesome addition to the party. I definitely do NOT claim to be a baker or cake decoration by any means, but I was pretty impressed with my creation. I stacked round cakes, frosted them, and used peanut butter wafer bars, Swiss Cake rolls and Ding Dongs along with Angry Birds stickers taped to toothpicks to decorate my structure. I found the Angry Birds pig erasers at Toys R Us. Check it out!