By way of Michael Silence, here's the STS-116 Mission Blog by Space Shuttle pilot Bill Oefelein.

Space Shuttle trivia: IBM ThinkPads are the official laptops aboard Space Shuttle missions. Designated PGSC (Payload and General Support Computer), they are mostly off-the-shelf ThinkPads modified for such things as cooling (heat doesn't rise in zero G), power supply, and interfaces. Here's an interesting article about an earlier version and the modifications required.

NASA now uses a modified ThinkPad A31p model. A Space Shuttle mission has six or more ThinkPads on board. STS-114 Discovery flew a total of nine ThinkPads, including six of the older 760XD ThinkPads (with Windows 98!) and three A31p models with dual hard drives that could be booted into Windows 2000 or QNX. A31p ThinkPads are also used on the International Space Station.

They have bitchin' Wi-Fi, too. In 1998, Astronaut/Senator John Glenn exchanged emails with President Clinton from on board STS-95 using a wireless Microsoft NT 4.0 network and Exchange Server.

Since then they've added VOIP so astronauts can phone home. It works over NASA's Orbital Communications Adapter (OCA) which was designed to overcome propagation delay that would normally break TCP/IP.