ADB - http://developer.android.com/sdk/index.html or refer to How to install and use ADB
Fastboot - http://developer.htc.com/adp.html#s2 (Select the right fastboot for your OS) (Should be part of the Android SDK in the Android SDK Root/Tools folder, if not download it here)
Motorola Drivers - http://forum.xda-developers.com/showthread.php?t=981578
Mac Users This guide was written/modified assuming that the name of the fastboot file is fastboot-mac (downloaded from the HTC Developer's site). If the fastboot program you're using is from the Android SDK or downloaded elsewhere and is named simply fastboot, omit the -mac part (or follow the directions for Linux users when it comes to using fastboot)
1. Download the items you need from the What You Need section
2. Open a terminal (located in the utilities folder for Macs) or cmd in search box on Windows.
3. Navigate to your sdk/platform-tools folder (not required if configured into the PATH environment variable)
In Mac and Linux
and make sure your Xoom shows up on the list.
This command will show you if your device is connected to the Android Debug Bridge.
5. Now type:
In Mac and Linux
./adb reboot bootloader
adb reboot bootloader
(You can skip the next 3 steps if you’ve unlocked with fastboot previously)
This will reboot your device into bootloader mode accepting fastboot commands.
6. I had to type this first to get fastboot to execute (Mac and Linux):
chmod 755 fastboot-mac
chmod 755 fastboot
This will change the permissions of the FASTBOOT BINARY so it can execute.
7. Now type:
./fastboot-mac oem unlock
./fastboot oem unlock
fastboot oem unlock
Once you run one of the commands above, your Xoom will present you with a warning screen. Press Volume Down to Accept then Volume Up to confirm. You'll then be asked if if you're sure, press Volume Down then Volume Up again to confirmed. This will unlock the bootloader and reboot the Xoom.
Upon unlocking the bootloader, this will allow your Xoom to be "hackable" but will VOID your warranty, even if you relock the device. If you'd like to re-lock it later you can refer this guide.