How can I copy the blockchain from my working client for use with a live CD savings wallet? I have the Bitcoin client installed on my Windows PC, but I want to set up a savings wallet with better security that I access with an Ubuntu live CD. I don't want to have to download the entire blockchain though - can I use my blockchain from Windows in the Ubuntu OS?

And how can I copy the blockchain from my existing Windows client installation to, say, a USB stick for use by an Ubuntu live CD, then into the Bitcoin client folder?
You can find the blockchain in this directory:

C:\Documents and Settings\YourUserName\Application data\Bitcoin (XP)
or
C:\Users\YourUserName\Appdata\Roaming\Bitcoin (Vista and 7)

As blk0001.dat and blkindex.dat. Copying those files to a proper folder on your Ubundu (~/.bitcoin/) should spare you from redownloading the entire blockchain.