I want to buy just the wireless card that comes internally in most laptops today. Also what interface do they use (i.e. PCI etc.)?

it am not sure I understand what you are shopping for. Space inside a laptop is very tight. So in order to get a card that fits we would want to know the barand and model.
If you are wanting to surf the Internet, email and online chat while near a wifi Spot this is the easiest and most cost effective method to provide wireless access to your desktop, notebook

• Netgear Wg111v2 Usb Wifi Card Includes Driver Cd and USB Extender
  NetGear 802.11g 54Mbps Wireless Usb 2.0 Adapter WG111v2 * Good for surfing the Internet, email and online chat * Provides wireless access to your desktop, notebook or public Wi-Fi hotspots

another option is

• SanDisk Connect SD Wi-Fi card Network
  The Wi-Fi SD card is the smallest Wi-Fi card in the market. The card will allow SDIO enabled devices to connect to HotSpots (802.11b Access Points) worldwide for fast wireless Internet connectivity. The card supports Pocket PC 2002, Pocket PC 2003, Windows Mobile 2003 and Palm Zire 71 devices that have an SDIO enabled slot.

or

• BELKIN F5D7010 Wireless Notebook PCMCIA Card
  The Card sets up on any notebook PC, with the simplicity of Plug-and-Play http://www.technology.It slides easily into any 32-bit CardBus slot to enable a wireless connection to your network. The Card uses the wireless 802.11g 2.4GHz standard to offer you the widest working range-up to 1800 feet-and greater interoperability in mixed networking environments. 802.11g is backward-compatible with the 802.11b Wi-Fi networking standard,