International Cell Phone Rental, Satellite Phone Rental
Try these guys. They have gsm global phones and sat phones, but sat phones are only from Iridium. I have not had great luck with Iridium since I have had connection problems in the past. Looking at the post left before me they indicate on the site that they have improved on Iridiums service.
I usually go with sat phones and prefer globalstar.
Satellite Phones by Globalstar and Iridium - Phone Products and Rentals at GlobalCom