This is easier than you might think. Just sign into your Dropbox account on the Web, then click the Getting Started tab. Complete five of the six listed "startup" steps (some or all of which might already be crossed off) and presto! You've just earned an extra 250MB of storage.
Don't have a Dropbox account yet? If you don't mind a little nepotism, use my referral link and we'll both get an extra 250MB -- meaning you can actually get a total of 500MB of extra free storage. (Then be sure to hit Dropbox's referrals page to enlist your own friends, co-workers, etc. -- and net another 250MB for each person you bring in. Before you know it, you might have five or six gigabytes' worth of free Dropbox storage.)
In case the name has someone failed to cross your radar, Dropbox syncs designated files and folders with the Web, your other PCs, your smartphone, and so on. It's insanely easy to use and incredibly handy to have around. To learn more, check out some of our previous posts about the service: