How do I turn FTP sharing on in Lion?
The option has been removed from the GUI in OS X 10.7 however you can enable it with a few commands. 

Here is a good write up on how to do it. 

http://reviews.cnet.com/8301-13727_7-20088844-263/managing-ftp-services-in-os-x-lion/

Summary of the link above: 

To Load: 

sudo launchctl load -w /System/Library/LaunchDaemons/ftp.plist


Then to start and stop you would run the following: 

sudo launchctl start com.apple.ftpd

sudo launchctl stop com.apple.ftpd


To Unload: 

sudo launchctl unload /System/Library/LaunchDaemons/ftp.plist