status.build.phonegap says the servers are down, no idea why though.
Just came here to report this. I have been using build to create my app and can't do anything today.
No response in hours is not a good sign.
It's the same thing every time: no announcement in advance, no official reaction during the downtime, even after several hours.
I would suggest installing a local install of the PhoneGap CLI and any associated SDKs you need. Then you can build locally. There are lots of ways for cloud services to be down, so it never hurts to have a local backup option.
If I had to guess, the weekend isn't helping response; my guess is things will be back sometime after 8am PDT tomorrow. I sent a tweet, but given the weekend I don't expect anything until tomorrow.
Also moving this to the PGB forum.