We get asked about co-registration quite a lot, so I thought I’d post this link over to an article from Nick Usborne at Excess Voice on the topic (you’ll have to scroll down on that page for the article).
For those who don’t know, co-registration is when you sign up for one list, and during the process, you’re given the opportunity to sign up for other related lists. It’s a nice way to grow your subscriber base. Mr. Usborne uses co-registration himself, and apparently it works. Very well. He also includes some tips on selecting a partner, and bartering content.