Freebbble!

IsometrIcon – Free Photoshop Plugin is a free Various design resource made by Dribbble user Michael Tzscheppan. As far as I can tell, its license is Unknown.

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.