Yes, I have done this. Whether or not you are charged a fee (from the resort) depends on where you are staying. Some of the resorts that have a conference center charge $10 I think. I know that BCV charges & the other ones that have already been mentioned. However, I still think its worth it to save on luggage fees! Plus, some of the Disney resorts do not charge a fee. I shipped a package to myself last year to AKL and I wasn't charged anything. I sent a HUGE box to myself...filled with diapers, wipes, jars of baby food, disposable bibs, disposable cups/spoons/forks/bowls, shampoo/conditioner, baby wash, etc. I filled up a large diaper box full of these things & it was fairly heavy. From PA to FL it cost me around $15 and I shipped it Priority Mail. I really think it saved on luggage space as well as fees & it was great to know those items were already at the resort waiting for us to arrive!
It was a simple process. I called Guest Services to confirm the process, but basically you just ship the box to yourself at the resort. It helps them a lot if you put the following:
Your First & Last Name
Reservation Number & Arrival Date
Resort Name
Resort Address
Once they receive your package, they "link" it to your ressie in their system. As soon as you arrive, they get the box. I didn't even have to ask for mine, the CM said "Oh, I see you have a package" and went to get it immediately. I was very impressed with the check-in process & how easy it was.
I will be shipping myself another package this year & am thinking about buying a return label as well to ship stuff back home once we are in FL!!! I hope this helps, please ask if you have any other questions!