This one'll be short, in the interest of posting before all the fun starts! We've opened up two new email domains, @ymail.com and @rocketmail.com, so that you can finally grab that email address that you've always been hoping for (because sean@rocketmail.com is easier to remember than xxXSean67723Xxx@yahoo.com). The domains apparently open up somewhere around noon PST today, and as far as I can judge, you need to set them up as new Yahoo! accounts. We'll find out together whether there are any options to merge accounts together or claim addresses from existing @yahoo.com accounts. So, just be sure to roll out around noon and stake your claim on this pristine email frontier before all the good names are taken again. :D
EDIT: Word of warning -- if you get an email address that's TOO popular (ie, sean@ymail.com), do keep in mind that you're opening yourself up to more potential spam, since you'll have an easily dictionary-guessed email address on a popular domain. We have pretty solid spam blocking, but it can only do so much.
EDIT #2: Here's the official signup link: http://new.mail.yahoo.com/addresses
EDIT #3: This, of course, means that you can use either http://ymail.com or http://rocketmail.com as shorthand for http://mail.yahoo.com, which is kind of handy. And, on that subject, does everyone remember that you can type http://ysearch.com instead of going to http://search.yahoo.com? Goooood.
Also, the official Yahoo! Mail blog post on this subject is available here.