Neowin has posted instructions on how you can register a live.com ID at Microsoft, it's a few simple steps and after that you will maybe snap up an ID that's not already registered to someone else. I got mine and have verified that these steps do in fact work. Enjoy!

How to get a Live.com ID:
1.Go to https://accountservices.passport.net/reg.srf register an passport account with a NON-HOTMAIL/MSN email address
2. Sign in to http://login.live.com with your passport that you just registered.
3. Paste https://account.live.com/EditProf.aspx into address bar.
4. Edit your registered information, input your birthday (18+) and change your Country/Region to 'United States'.
5. Paste https://account.live.com/LoginChangeName.aspx to address bar, then your can change your passport to @live.com.

Note:
- If you do not change to US (skip step four), you'll get @windowslive.com domain address
- If you change to 'China', you'll get @live.cn domain address
- If you change to 'Korea', you'll get @live.co.kr domain address and so on...
- It seems like Windows Live Mail only works with @live.com addresses at the moment
- Please note that after migrating to @live.com domain, your previous NON-HOTMAIL/MSN email address will no longer be associated with passport
- Currently, it only works for NON-HOTMAIL/MSN email addresses (in Step 1)