I almost always tip the maid, usually around $5/day at high end properties. I try to leave a tip every day, although at many properties the maids will not take the tip unless they are absolutely certain they are for them.

I do not tip the doormen for holding the door, and usually not for hailing cabs, but when they help me load and unload luggage, I tip them like I would a bellman (usually $5, although I'll tip the bellman $10 if I'm traveling with my wife and daughter and we've brought all of our worldly possessions).

I'll also tip the concierge, up to about $20, for scoring a hard-to-get ticket or reservation.