Evernote, the brain-expanding data organiser, was one of our original suggestions on where to go when Google Notebook goes down. Luckily, the service's coders see it the same way. As explained at their blog, jumping from Notebook to Evernote requires grabbing an Atom-formatted export of each notebook, one by one, then heading to Evernote's Google Notebook import page. Once they arrive, your notebooks' creation dates, URLs, images, and other metadata should arrive intact, and labels and sections become tags.
Over at Zoho Notebook, importing your notes requires a (direct link ahoy) Firefox plug-in. Once it's installed, however, it's real easy — open up two tabs, log into Zoho in one, Google Notebook in the other, then open a third tab and paste in this URL:
chrome://zoho-notebook/content/g2z.html. That should launch an importer that does the tough work for you. Zoho Notebook added a "Text Page" that looks similar to Google's layout of cascading vertical notepads.
For more places to stash your orphaned notes, check out our suggestion list. G-Notebook users, which service have you ended up migrating to, and why? Tell us in the comments.