Verizon Wireless/Motorola are currently rolling out the infamous Android 3.2 upgrade right now. Go to settings, about, and system update. After you take the update you’ll have access to the SD card slot. We know, we know, we can’t believe that the SD card slot didn’t work when you bought that shiny new Xoom, but rest assured it does now.
You’ll also get the newest feature of Android Honeycomb which allows you to resize apps not designed for Honeycomb to look a bit better on the tablet.