As far as I know, there isn't a consistent one. The Wall Street Journal recently increased the level of protection their paywall provides. Some have reported success using the "web" link in an private browsing window.
Edit to add: I had forgotten about the hack my sibling mentioned. Thanks, 'ayw!
http://facebook.com/l.php?u=https://www.wsj.com/articles/sca...
and just click to follow the link. If the referrer is facebook, they let you through.