The Elder Scrolls Online, you have already heard about it and if not, you're freaking out, opening another window and looking for it right now. Needless to say I dropped everything I was doing and went right away to work on signing up as soon as I saw it pop up in my facebook news feed and then watched the cinematic trailer that was released with the announcement after.
The beta sign up page is pretty straight forward and had the nice touch of offering a "current closed beta selection chance rating" meter that increased depending on the amount and information you gave.
My raking was "above average" and I haven't seen or heard of anyone else getting anything other than "average" and "above average".
You will need to give information on your system and have the option to write more if you like. You are also required to sign a NDA (non disclosure agreement) that includes not being able to inform others if you have been accepted in the beta and being over the age of 18.
Terminus Zaire over at TESOF (TESO Fan forum) has put together a nice post giving you the terms of the NDA in simpler English: The TESO Non-Disclosure Agreement: How It Impacts YOU! If you're even remotely interested in the Beta and/or already signed up I suggest you check it out if you didn't quite understand it the first read through (or if you're one of those naughty people who agree to things without reading them).
As stated on the sign up page check your spam folder if you don't receive a confirmation! I used a more secure email address to sign up for the beta (I always do for MMORPGs to help keep away the pathetic phishing attempts emailing the wrong address) which gets forwarded to my more public email and I didn't receive anything. 2 hours later I logged into the more secure one and found it hiding in the spam folder (so it never got forwarded to the other email address which I check all the time). The email took a while to arrive as well (there is no doubt high traffic for the sign ups). The email address is firstname.lastname@example.org, so you can add that to your contacts, but I also noticed a secondary email address attached with it that did look iffy (via amazonses.com) and probably why google marked it as spam, so keep an eye on your spam folder.
There is now a Beta Sign up FAQ page you can check out if you have any other questions: The Elder Scrolls Online Beta FAQ.
Good luck to all of those who are interested and signed up for Beta testing! Just remember to keep your mouth shut if you get in! ;)
And now here is the Cinematic Beta Sign Up trailer that was (oddly) posted by so many other people before posted from the official youtube page (this is the official video).