A number of companies produce wireless networking kits. These kits are essentially a bundle containing an access point, two wireless PC Cards or wireless USB connectors, software drivers, and instructions.
For example, for around $50 from a discount retailer, you can buy the D-Link DWL-920 kit, which includes an 802.11b access point and two USB 802.11b connectors.
Microsoft's Wireless Desktop Kit MN-610 sells for about $130, and contains "everything you need to set up a wireless 802.11b network" for two desktop computers. Essentially, the contents are the same as the D-Link kit: an access point and two USB wireless connectors. (Yes, the Microsoft USB adapters have a larger form-factor than the D-Link units, and may have a greater range.)
There's nothing particularly wrong with these networking kits, but they don't get you very far. Although the Microsoft kit is a little on the expensive side for what it is, the D-Link bundle might actually save you a little money over buying the pieces separately.
Don't get me wrong I'm all for anything that will make life simpler for you. But in this case, wireless networking kits don't bring much to the party. You can start with one of them, and expand your network later if you want. Still, it is no more complicated to buy an access point and create your own "kit."