What I do is, after I include the url of the site I want to promote in my Resource Box, I add a second line that simply says " Remember To Add Me On Facebook". This, as I have noticed, increases the likelyhood of readers joining your related fanpage, since social media is the IN thing these days.
Try it and see if it works for you. Have a great weekend!
P.S Remember to include your URL in your fanpage/Facebook profile as well