IHotelier is a nice Flash MX reservation interface. See for instance how, once you've selected a room type, availability is instantly shown in the calendar. Constraints are well enforced so that you can't add more rooms than available in the chosen time period, or put too many people in the room(s) you picked. The "Finish Reservation" button will enable itself only when all fields are filled out. In the meantime, there's a roll-over message on it to point to what's missing. The way prices are shown in the calendar makes it real easy to adapt your stay to your budget (prices being very volatile for yield management purposes).

Very well executed overall. I'd like to know how much more business hotels will get thanks to this.