Response code 503?
Edit: Oh right, restarted the application and yeah, won't connect to minecraft.net
The 503 error is because (I think) minecraft.net is down, and the server verifies your user name with minecraft.net to make sure you're not pretending to be someone on the whitelist.
I shall turn off that check now and you should be able to log in if you do 'play off line' when you load minecraft.
http://www.next-gen.biz/news/minecraft-coming-to-ios
But no mention of Android :'(
If you still can't log in, the new launcher (which uses HTTPS) seems to still be working. Can grab it here:
https://s3.amazonaws.com/MinecraftDownload/tmp/MinecraftLauncher.jar
That is the beta/leaked one that Notch linked to on Twitter on Friday.
The 'official' one came out today, just before minecraft.net fell over :D