Install Backtrack 3 on USB
Here are some pretty easy steps to install Backtrack 3 to your USB drive.
Go to Offensive-Security and get the Backtrack 3 Beta USB rar file, about 946 MB in size.
I got on my Windows XP machine and used WinRAR to uncompress to a folder on my machine.
Copy the BT and BOOT folders to your thumb drive.
If you are on a Windows machine, go into the /boot folder and run bootinst.bat, if you are running Linux or OSX run bootinst.sh. This will set your thumb drive to be bootable.
I am running BT3 on my Dell E1705 laptop with Compiz running. In the grub, it says that this is experimental, but I have not seen any errors as of yet.