Zumbox is neat. It's like Gmail, but for snail mail. To get an inbox (it's free!), all you need is your regular address. Then, when anyone who sends a letter to your address using Zumbox, it shows up in your inbox. Confused? This picture kind of clears everything up:
As you see, it gives you all your messages in neat little envelopes. When you open one, you read the message, then file it, delete it, or whatever. The cool thing, of course, is that its digital. You can set up filters, block senders, and more. Also, it is a lot cheaper than standard mail. Businesses can send out letters to huge mailing lists for just a few pennies each. Also, individuals can send a letter for $.05. Remember, this doesn't replace standard mail. It is only based off of it.
Overall, I'd say its cool, but there is an issue: Why would I pay to send a digital letter when I could just send an email for free? Now, there are some cool things that you can't do with either snail mail or email, like embedding flash, but these are things the average person isn't going to need this. My suggestion: get people to like this, and let them do everything for free, then make the corporations pay, since this is a lot cheaper and easier for them to connect to their customers.