I used this blog to help me make a beautiful chalk sign on my computer using only powerpoint and thought I would share. It turned out so great!
http://www.ourhomemadeeasy.com/diy-birthday-chalkboard/

Here is how mine came out-- (I took off his name for privacy)

I hope this will help anyone else who might want to make one. It took me an evening of fiddling around with it, but it was fun!