FrDave had a great post recently about a way to incorporate prestige classes. Essentially, he moves prestige classes to entry at fourth level, so that a character has to survive and be a hero before he is able to select some of the more obscure classes. FrDave also comes up with some interesting specialist classes as the prestige class, for example healer for cleric.
Musing on what he had posted, I thought of the graphic below, which essentially shows a decision tree of the various "career options" that a standard human has. I am no Telecanter, so it is a bit crude.
[Apologies on the format, but I knocked it out in MS Word, and then cropped a screenshot to get this image]
Obviously this needs some work, but I think it gets the concept across. It could be modified to show the classes allowed in YOUR world, and with a better presentation, could have all of the spell levels and skill information included as well to allow for it to be a one stop visual representation of player classes. You will note that in the cleric and fighter rows, I started to go that direction, so it shows the XP and HP of each character level.