While doing it I also found two other ways to increase space: https://www.dropbox.com/free just have to connect twitter, fb, and a couple of things.
If you have referrals and a .edu email address you can also get double referral space here https://www.dropbox.com/edu It even gives you credit for the referrals you've already sent.
If you don't have a .edu, there was a thread around here somewhere that posted a place to get one.