Re: Travel: You may want to have your own company's travel agent book air travel, car rental and hotels. Part of the contact should include the statement that consultant's will be bound by the same travel policies as employees (no limousine service or penthouse rentals) along with a copy of that policy.
You may want to specify the number of trips home per month you will pay for. I have worked with some contractors where I pay for two trips home per month and the vendor pays for the other two (in a four week month).
If you have a cafeteria plan (not normal but I have experienced them in Europe) you may want to provide for the contractors' access. You really gain in time saved when people can eat in the building. On the flip-side,you may need to inform them that 10am and 3pm coffee breaks are for employees, as are birthday celebrations, etc. This is very sensitive. Some employees resent contractors' presence and really resent them showing up at monthly birthday celebrations. The flip side of this is that you are using knowledge workers and want them pleaseed to be working there. It might be worth it to find something you can reserve for permancent employees.
Working outside "normal" work hours. This is almost ludicrous when thining of IT shops but it can come up. If the contractor isn't going home every weekend s/he may want to work on your project. Do you need an employee supervisory presence? Special passes into the building? How about daily, outside normal work hours?