Here is an extensive list of brand sites on Foursquare - check out the list and follow your favorite brand!
I found a fantastic list provided by TheKruser.com, take a peak and follow your favorite brand. Some badges require you follow the brand. I am now following the Wall Street Journal, The Today Show, Comedy Central, People Magazine and Colorado! Enrich your friends and followers on Foursquare with over 100 interesting brands!