Go out an buy "Setting Solutions" by Sharyn someone. Let me look it up. everyone should have this book. she shows you how to set odd size blocks, odd numbers of blocks (like 17), odd color blocks. Well, you get it.
edited to add, here's the amazon listing
http://www.amazon.com/Setting-Soluti...5870227&sr=8-1
author is Sharyn Craig
worth every penny