Actually, all my work is under the Creative Commons Attribution-Noncommercial-Share Alike 2.5 Canada (cc-by-nc-sa). In short, you can modify and change this as well as redistribute as long as it is non-commercial and is released under the same license.
What's the difference?
It is basically the same as Titi's suggestion of cc-by-sa, except that it does not allow commercial use without permission. However, like all the terms in the license, this CAN be wavered by simply asking permission (I'll probably say yes, but I would like a free copy). In short, you can do whatever you want with this WITHOUT having to ask for permission as long as your work is free, released under the same license, and you credit me.
Cheers to Creative Commons!