Yeah which is fine; I just remembered another Python notebook environment but that might have been just this one :) Unfortunately I don't get to work with Python much.
Wakari is much more than just "IPython notebook in the cloud"; however, we do have great support for it. For instance, we have just recently enabled a feature which lets you host & share your IPython notebooks: http://continuum.io/blog/ipython-notebook-sharing-in-wakari
Right now Wakari is in closed beta, meaning you have to register and we manually approve accounts (which we do very quickly).
The IPython notebook came after the SAGE notebook, but it seems to be gaining popularity faster in the broader scientific Python community. (The SAGE community tends to be more oriented towards pure math.) SAGE is a very powerful system and introduced many cool things very early on, but it definitely is a bit of its own island in the scientific python landscape. I don't know if that's because of the licensing (it's GPL) or the software distribution logistics or what.
