OtherInbox is a service that helps with one of the growing problems of using Web services: e-mail overload. More specifically, services that take your information and sell it to third parties--thus filling up your in-box with decentralized junk.
OtherInbox works by giving you a special address you can use when you sign up for things and it helps you filter them in a central location with tags and layout akin to Apple's Mail application. Each "subscription" reads like its own in-box.
The service may be most useful for figuring out what services are selling out your e-mail address to other parties, but it's also good for handling bacn--the messages you may want from a service, but not necessarily filling up your in-box. What makes it special is that users can effectively kill off that special address making the messages bounce back to the people who would be spamming you.
One thing to consider is that you can currently do this with Gmail. I do this with my in-box by adding a +servicename after my username, coming out to something like Yourname+Amazon@gmail.com. That way you can phase them out completely using a simple filter if you start getting spammed. OtherInbox offers you a little more security with its block feature, and the fact you're basically signing up for another address.
The service is currently in private beta, but made its public debut at Monday's TechCrunch50 conference. On a side note: you need to provide OtherInbox your e-mail address when you sign-up. And we have 25 invites to give out--so go here to get yours while they last.