I don't think there any Netduino specific WiFi shields. Look for an Arduino shield. Here is one,
The problem with these shields is that the drivers are Arduino specific. This is a Netduino project using an Arduino shield with Netduino drivers,
But, expect to be frustrated with these shields because you need to talk to them over SPI. However, You don't need a WiFi shield. The Edimax simply turns your Netduino ethernet port transparently into a wireless connection; thereby avoiding all driver complications. After you configure the Edimax for your network, connect its ethernet port into the Netduino ethernet port, provide power to the Edimax and the Netduino will be connected to your wireless network. Also, another advantage is that you do not tie up any SPI pins.
If you want a stack arrangement,, just get a protoshield and affix the Edimax to it. The Edimax will fit exactly between the headers without any modification.Go to the full post