I am using the free youtube downloader. It works great and also allows you to download from a lot of other sites. The sites that it doesn't handle the free Real Player seems to fill most of the gap.

the youtube downloader has over 61,000,000 downloads which means you know it's going to be safe and works good.

I always download from cnet if possible to prevent malware.

http://download.cnet.com/YouTube-Downloader/3000-2071_4-10647340.html?tag=mncol;3