I needed to move some data from a legacy application into GnuCash, so I wrote a really small Java package to make the job, which I wanted to be separate from my application, so that I can publish my (small) work here.
This package allows to generate files in the Quicken interchange format (QIF), which is a specially formatted text (ASCII) file that lets you to move transactions. Although it is only a tool, this package might help some people to understand the Quicken interchange format.
You can read more on the package by accessing its javadoc, which contains example usages, as well as screenshots of GnuCash showing some importations.
The very first release is available here. A web access to the CVS repository is available here. If there is any interest for it, I might set up an anonymous CVS access. If you are interested in developing this package, please contact me.
This is all open source, available under the terms of the General Public License