Sometimes it's a good idean to add a subscribe form to the unsubscribe page, and give the possibility to the customer to choose another list or another frequency.
I try to get the e-mail address on the unsubscribe page, to help the customer and let it choose only the list which he want to join, without need to write his e-mail address.
Is it possible?
Yes! You can do that. There's two things you'll need to do. First, you can change the settings in your account so that when people click on the unsubscribe link they are redirected to a page on your site. On that page you can place a link to the subscribe form, or include it right there for them to get back on your list. See this help page for more info - http://help.campaignmonitor.com/topic.aspx?t=187 .
Second, you can provide a link in your emails, preferably near your unsubscribe link, where your recipients can change their preferences, such as which lists they would like to be on by topic or frequency. This page has more details to get you started - http://help.campaignmonitor.com/topic.aspx?t=113 .