There are a number of online programs available that will capture YouTube and Google Videos. Some will be able to save directly into a format that will play on an iPod and others may need to be converted to a different format once it is downloaded. You might want to take a look at http://vixy.net/ an Online FLV Converter where you can download online videos direct to PC / iPod / PSP or http://keepvid.com/. If those don't work for you try googling "capture youtube video".
They are not likely to work on videos hosted on Ning, but should work if the videos are from YouTube or Google Video and just "embedded" at Ning. The key then would be to get to the original YT or GV URL for the video. If you click on the "Embed Code" button on the Ning video page, in that code will be the original URL for the host.