I agree with everything that Greg and Treewind say. I like a CD to feel like a complete, finished piece of work, so the running order is very important. I made a point of not putting funny songs at either the beginning or end of mine. I felt that if people were expecting a comedy album, they would just turn off as soon as something serious came along. Making a CD is a bit like creating your own little world. You have to lead the listener through it to some extent. Your running order is vital in making them want to keep on going to see what comes next.