Ideally, IPython itself shouldn't crash. It will catch exceptions produced by you, but bugs in its internals will still crash it.
In such a situation, IPython will leave a file named 'IPython_crash_report.txt' in your IPYTHONDIR directory (that way if crashes happen several times it won't litter many directories, the post-mortem file is always located in the same place and new occurrences just overwrite the previous one). If you can mail this file to the developers (see sec. 16 for names and addresses), it will help us a lot in understanding the cause of the problem and fixing it sooner.
IPython also has an online bug-tracker, located at http://www.scipy.net/roundup/ipython. In addition to mailing the developers, it would be a good idea to file a bug report here. This will ensure that the issue is properly followed to conclusion.
You can also use this bug tracker to file feature requests.