These days, you can easily set up IPython Notebook on a VM with any of a number of cloud service providers. EC2 has been done a bunch of times and is well documented, but pretty much any service that you can run a full Linux VM on should work.
It works like a regular webapp. Your code runs on the server, so you can't program your Chomebook, just the VM, but that's better in a lot of circumstances.
It's one popular option, even with people who have IPython installed locally, just because Cloud, but on Chrome OS, it makes even more sense to look at trying to get something like that set up, even if you use one of the other options to code offline.
