Where can I find a cake serving chart?  I know that wedding cake servings are smaller, but I would like to have a reference for general serving sizes.

Here's a thread that might help you. The 2 most popular are Wilton's (typical 1"x2" servings) and Earlene's (a little larger).

http://cakecentral.com/t/611330/best-party-cake-serving-chart