I’ve created a new category/page for all JNLP Creator stuff.
Almost complete now, still has a few missing features (e.g. no way to add the JAR files for your app yet; e.g. although it can add extensions, if you try to edit an existing JNLP file, then it doesn’t load them from the source JNLP) and a few bugs (requires Java 1.6 to run, sorry).
But the core stuff is there, and it has some nifty stuff e.g. with one click you can test your file locally using the actual data, which mostly works (although c.f. the lack of resources issue above! This is definitely still an alpha build).