With out STD's officially order it was time for me to start tracking down addresses. (What? You don't remember me posting our final STD? That's because it hasn't happened yet. :D) Anyways you could always do the easy way and call people up, or facebook them, or e-mail them. That would get you exactly what you needed. Except you would them have to retype them up again to get them all into a spreadsheet so they'd be easy to use.
Or you could use the other way, and force your guests to do the work. :D Enter google docs... Basically I referenced this post by Ms. Fondue and this post by Mrs. Pashmina. Although honestly it's so easy you could basically do it without instruction. All you're really doing is going to "Forms" to create something resembling this.
From there when people enter their information and hit submit, google collects it all in a spreadsheet. I was originally planning on screenshot of the empty spreadsheet as well, but only 2 hours after hitting send I've already had 7 different people respond. Hopefully this pace holds up!
The one catch with this process is that you at least need an e-mail address. I was able to get quite a bit from facebook stalking, but it looks like for the rest might require a phone call or two.
How did you go about collecting mailing address for your invitations? And which side of the Backstreet/NSYNC battle are you on?