What a shame. Google has shut down Google Notebook.   (They actually shut down several sites/services, but Notebook was the only one I used.  See a wrap up here.) I love Google Notebook, and I'm pleased to see they will continue to offer it to those of us that have used it for awhile, but they will no longer update it, or offer it if you're not already signed up.  You might try signing up today, just in case you want ti at some point in the future. 

This is a shame.  My first Google disappointment in a long time. 

I've got a Beta invite to WebNotes.  I've been meaning to try it, but been busy.  I'll try it soon and report back.   You can also read my review of Notebook and competitor Zotero here