There is so much to do! Cake, pick out invitations, table centerpieces, favors, photographer (that one took me forever and you need to book them ahead of time to make sure they aren't already booked up), honeymoon arrangements if you are going on one, ummmmm.... oh! Hair styles and stylists, makeup, jewelry, shoes, music (during ceremony and reception)... that's all I can think of for now, but I'm sure I'm missing stuff!
Oh and also, if you are getting a grooms cake that isn't obviously a part of a wedding (like ours had a pool ball theme), if you tell them it is for a birthday party I hear you will get it a lot cheaper. I found out too late for mine, so I haven't tested that theory, but I was told they jack up the price as soon as you say the word wedding.