Here is a brief list of other projects using IPython. If you know of more, feel free to add them.
Scientific computing projects
The PyRAF environment for astronomical image analysis, from the Space Telescope Science Institute, will include in its next official release an IPython-based interface. Currently (May'05) this functionality is only available via SVN PyRAF.
The CASA interactive shell from the National Radio Astronomy Observatory is built on top of IPython.
The Ganga system, developed at CERN for Grid job control for the LHCb and ATLAS experiments, uses IPython for its CLIP interface.
SAGE, a system for algebraic number theory and arithmetic geometry, uses IPython for its interactive command-line interface.
Singular, another computer algebra system, also offers an IPython interface (Singular is also accessible as a SAGE subsystem).
The Pymerase project for microarray gene expression databases, exposes an IPython shell in its iPymerase mode.
The PyMAD project, where IPython is used to control a neutron spectrometer at the CEA-Grenoble and the Institut Laue Langevin in France. A Wiki is available detailing some of the new features introduced in IPython to support PyMAD (as well as PyRAF). This may be of interest to those who wish to embed IPython in complex environments.
Web frameworks and other systems
The Pylons web framework can optionally use IPython if installed.
As of Jan'06 (Changeset 1930, to be precise), IPython is the admin shell for the Django web framework.
You can use IPython to debug Zope and Plone, as explained in these two pages.
The Schevo database can be explored with IPython.
The Axon Shell in the BBC's Kamaelia project is an embedded IPython instance.
As of revision 53 (Oct 11/05), the new Turbo Gears framework can optionally use IPython as its shell. This post has some details on how it works.
Movable Python, by Michael Foord and Bruno Thoorens, is a way of building portable Python environments which uses IPython for its interactive features.
The Logix programming system integrates with IPython for interactive work.
The iVR toolkit provides IPython as its shell in interactive Virtual Reality applications.