Here is my take:
• Bellman: $1 to $2 per bag - sounds about right.
• Concierge: $10 to $20 for performing a special service, such as scoring tickets to a sold-out event or wrangling lost luggage from your airline - sounds about right.
• Doorman: $2 for hailing a cab in rush hour or in the rain; $1 for each bag - this is OK if it requires actually stepping into the rain or hailing the cab in the street; however, if all it takes is to raise a hand/blow a whistle to get a cab parked a few feet away then I typically don't tip.
• Housekeeping: $5 to $10 per day. Leave it at the front desk if you want it divided equally among all your housekeepers - this is too much IMO, especially during longer stays.
• Room Service: A service charge is almost always included in the bill. To personally thank your server, 5 percent will suffice - agreed.
• Valet: $5 when your car is delivered - depending on the level of effort it takes to get the car (how far it's parked, weather conditions, rush hour service, etc) and the speed of service (relative to the required effort) my range is anywhere from $0 (very slow service) to $10.