In a nutshell, ClaimSpace is a way to tag content that you have created as being your own.
Claimspace will enable you to say, 'I created this resource, wish to be recognized for it on these terms ___, and I hope you find it worthy of your attention. What do you think?' - Korby Parnell
You can read the full post to get a better idea of what it is and how it is used. Korby can do a hell-of-a-lot-better job describing it than I can. What I find interesting about it is that it may solve my LiveId problem.
I started using the MSDN forums and blogging while working at a former employer. At that time, I created a LiveId using my company email account. I have since left, but all of the content that I created is still attached to that LiveId with no way to move it over to my personal LiveId or the LiveId I have under my new employer's email address.
I'm hopeful that with ClaimSpace I'll be able to tag all of my blog entries, forum posts and any other "content" that I create with a single, universal "token" that will allow readers and others to know that it all came from the same person.
This will also aid in discoverability. If I find a well thought-out article by an author that is new to me, I can use CardSpace to find all of his other articles.
This seems like it will go a long way to finding and promoting good content and recognizing those that put it out there. I'm on board with it when it finally arrives!