The main GoDaddy.com domain is unreachable and websites hosted by GoDaddy are also down. The more problematic part is that any domain registered with GoDaddy that uses its nameservers and DNS records are also down. That means that even if you host your site elsewhere, using GoDaddy for DNS means it is inaccessible.
On Twitter, Anonymous Own3r -- the security leader of Anonymous -- is taking personal responsibility for the attack.
@wordwhacker nah it's not Anonymous coletive the attack is coming just from me— Anonymous Own3r (@AnonymousOwn3r) September 10, 2012
Although not directly involved, Anonymous has also tweeted its support.
#TangoDown -- godaddy.com | by @anonymousown3r |— Anonymous (@AnonOpsLegion) September 10, 2012
Also on Twitter, GoDaddy said that it is "aware of the trouble people are having with our site" and that it is working on getting things fixed.
Reports on Hacker News also indicate that GoDaddy's phone support is also down.
As soon as GoDaddy returns, you might be interested in switching to a new registrar. This is how: