Many times when I am testing new OneNote code with SkyDrive and hit what I suspect may be a bug, I need to find out if what I am seeing could be explained if my computer running OneNote cannot communicate with the server. Monitoring network traffic via a proxy can help (think Fiddler) but even then if I get a "page not found" type of error it is hard to tell if that page really does not exist or if the network connection was down or if the server is otherwise in a bad state.
So here's a tip: SkyDrive has a service status web site that can tell you which of the many services they have are up and running. It is at https://status.live.com and for testing OneNote, SkyDrive is the most interesting to me. You can report problems here as well - always appreciated, by the way, so thanks if you do report and error and apologies if you have to report an error - and get a history of the past few months as well.
It is a useful page for testers and may be interesting to a wider audience as well. I have a favorite link added to my browser for this page and like I say, I keep my eye on it while testing.
Let me know if you find this interesting.
Questions, comments, concerns and criticisms always welcome,