You can't save videos directly on to your iPod Touch. You have to download them to your PC/Mac and then sync them to your iPod Touch using the iTunes software.

The most important aspect of this is to get your porn movies in a format that the iPod Touch can use, and be sure that your chosen porn service has it's movies in an iPod Touch friendly format.

I only recommend using a reputable, well known services to avoid the risk of downloading viruses to your PC/Mac.

Personally, I use the Brazzers Network. (Note: You need to click this link on your PC/Mac, as it will detect that you're using your iPod Touch and send you to the Mobile Version of the site. A pain in the ass!)

For information on downloading iPod Touch Porn, check out my blog at iPod Touch Porn.

Additional info can be found at: ipodhoney.com