We should mirror the functionality of creating PDF documents from Facelets templates and create a component set that generates excel documents. There are two approaches we can take. One approach is to use POI to build the document structure and then export it. The second approach is to build an XML document that Excel can understand. Technically there is no reason to actually produce a binary Excel document as long as we can feed something that Excel knows how to convert. Regular CSV support would be nice too, but I always find that to be such a cop out.
Creating this module shouldn't be too technically challenging since most of the infrastructure has been set up already when creating the PDF components. In fact, i would start by working in that module and then split it out into another JAR.
Some resource links: