Wave Toy Freebie
Available in PSD and HTML/CSS/JS version.
Wave Toy Freebie is a free Various design resource made by Dribbble user Diego Monzon. As far as I can tell, its license is Creative Commons Attribution-ShareAlike.
Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.