I've done this before with the peer-to-peer connection, but it isn't incredibly easy. You have to:

1. Turn on Internet Connection Sharing on the wired computer.
2. Set your Wi-Fi connection to use a static IP address in the same subnet as the wired computer (if it is 192.168.1.x, you need to pick an address also in 192.168.1.x). You also need to manually set the DNS servers given to the Wired Computer.
3. Set the default gateway for the wireless computer to the local IP address of the wired computer.

Somebody might be able to word this better and in a more step-by-step fashion, but basically, it's totally doable, but not a strictly simple process.