I don't know that I can give a *really* short description of MicroPlaza that does it justice, but I'll start by saying that it takes the links - short or otherwise - that the people you follow in Twitter post, and creates thumbnails out of them. MicroPlaza supports OAuth, so you can connect your Twitter account to it without giving away your Twitter password. You login and it shows you all the posts from the people that you follow that contain links. It also shows you any other Twitter posts that also link to that same item. You'll note from the screenshot below that multiple short URLs are being used, but MicroPlaza follows them all and figures out that they refer to the same page:
As I overlaid onto the image, @lauras is the person I follow on that list - MicroPlaza has included the rest of the people because they've pointed to the same thing Laura has.
Since it only includes Twitter posts with links, it's like a high intensity stream of information goodness. I very rarely go to the website, choosing instead to subscribe to an RSS feed of my public timeline. I first found out about MicroPlaza when Roland started sharing MicroPlaza entries in Google Reader - there was good stuff being shared, and the screenshot of the web page (plus the full title of the linked to page instead of just another short URL) made it easy to decide if the whole thing was worth reading. The commentary of all the people linking to the item makes for even more context.
Lastly there are tribes, where you can set up your own (private) groups of people in whatever orderings you want. For example, I created a Bootup Labs Tribe for the people and companies that are related to startups and entrepeneurism. This then groups the same links you're already seeing into these arbitrary groups. You do need to be following the accounts you want to group, since MicroPlaza has to have access through your own Twitter account. MicroPlaza is also creating its own public tribes, such as @topopensource, which follows a number of people and then lets you see the top open source links.
You'll need to follow @microplaza to get an invite code, or request one from me (@bmann). I'd love to hear your thoughts on your experience with MicroPlaza.