I usually tip the bellmen $3 per bag, but will generally round up to the nearest $5 increment so I'm not counting out a bunch of $1 bills.
I know I probably should, but I do not tip the greeter at the portico who helps you unload your luggage from the car onto a luggage cart. I only tip the bellman who brings the bags to the room. Maybe I'm being a jerk about it, but just because Disney's contracted certain functions and organized themselves in such a way that multiple people need to handle my luggage at check-in doesn't make me feel obligated to tip multiple times. I don't know if they pool these tips.
The one time I will tip multiple times for luggage is when we're changing resorts for a split stay. I will tip both the bellman who picks up the bags from the first room and the bellman who delivers them to the new room.
We always order something from the Disney florist, and the resorts have a runner who bring these around to the room. If we're in the room when they make this delivery, I always try to tip this person, but most times they will refuse to accept it.
If we run out of TP or request a blender and a housekeeper needs to run something to our room, I'll usually give them a few bucks.
Before we bought DVC, I would always tip the housekeepers a few bucks every morning. I had gotten out of that habit for some reason when we started staying on points, but recently started tipping the DVC housekeepers again.
We use a Tables in Wonderland card when dining, which adds an automatic 18% tip to the check. At home, I typically leave a 20% tip rounded up to the next whole dollar. Now, I don't add this 2% to every check, but I will often add something extra to the check for servers who did a good job.
About the only time we use valet parking is for TIW dining at a resort with valet service. I usually tip $3-$5 for this, depending on whether I have $1s in my wallet or if I saw the kid really running for the car. (Once, I accidentally left the keys to our car in my pocket at the Grand Floridian and the valet had to search the whole resort to find me. We were all the way out by the pool when he found us. I was so embarrassed, I think I gave him a $20.)
I don't tip the Magical Express drivers, personally, but's that's mainly because we never have luggage with us to be put under the bus. I do tip the RAC folks a couple bucks a bag when I drop them off.