I got an Arduino Uno for Christmas and just ordered this wifi shield, but I'd like to use it with an LCD shield. Can I just stack the LCD shield onto the wifi shield? Do I need any extra hardware to connect them?
The WIFI shield you linked to uses SPI, with two SS pins (One for the wifi, one for the SD card). It has a stackable header allowing the Arduino to pass through, so you can plug something in on top of it.
You don't mention which LCD shield you are going to use, or if it's really a shield at all. Adafruit has a 2 pin, i2c based LCD shield, which uses analog pins 5 and 4, which wouldn't interfere. There are LCDs based on i2c, spi, serial, and direct driving (8 or 4 bit), so it really does depend.
For reference, here is the wifi shield pin out, and the arduino uno pin out. You just need a lcd shield that doesn't use the SPI SS pin(s) as the Wifi Shield.
Some Arduino shields are made to be stacked and others are not.
You can potentially modify the shields (especially if you purchased them as kits) to be stacked or work together, but as mentioned, the schematics will be needed to determine how best to accomplish that.
Also don't forget to check the Arduino forum. Someone asked nearly the same question:
One user, estranged, did a little custom modding to arrive at this!