HSSF Alternatives to HSSF
Alternatives

Maybe it's unwise to advertise your competitors but we believe competition is good and we have the best support reading and write Excel workbooks currently available. This however does not purport to be a complete list.

Product URL Description
JSC jsc.tomschuetz.com Reading, calculating standard and VBA functions with Java at runtime.
Formula One ReportingEngines (division of Actuate Corporation) An alternative to this project is to buy the $5000 per server installation.
Visual Basic www.microsoft.com Give up XML and write Visual Basic code on a Microsoft Windows based Environment or output in Microsoft's beta and primarily undocumented XML for office format.
JExcel http://stareyes.homeip.net:8888 Frequently unavailable. Little currently known about it's capabilities.
JWorkbook http://www.object-refinery.com/jworkbook/index.html This effort supports Gnumeric and Excel, however the Excel part is done using POI anyway.
xlReader http://www.sourceforge.net/projects/xlrd Provides decent support for reading Excel.
Excel ODBC Driver http://www.nwlink.com/~leewal/content/exceljavasample.htm ODBC offers a somewhat wierd method for using Excel.
ExtenXLS http://www.extentech.com/products/ExtenXLS/docs/intro3.jsp Commercial library for reading, modifying and writing Excel spreadsheets. Not cheap but certainly a lot more affordable than Formula 1. No idea as to it's quality.
J-Integra Java-Excel Bridge http://www.intrinsyc.com/products/bridging/jintegra.asp Uses DCOM to an Excel instance on a windows machine.
Perl & C - There are a number of perl and C libraries, however none of them are consistent.
VistaJDBC http://www.vistaportal.com/products/vistajdbc.htm VistaJDBC driver works with both StarOffice and Excel spreadsheets and can access data using standard SQL statements without any API programming. VistaJDBC also implemented ability to choose by not just rows and columns but by specific cells, ranges of cells, etc.
Coldtags Excel Tag Library http://www.servletsuite.com/servlets/exceltag.htm This library outputs a simple CSV file, in which cells can contain numbers or text. You could output a CSV file without its help, but it gives a little more readability/structure to the code, and could be extended to handle more complexity. When you invoke one of these JSP pages from your browser, you open up an Excel spreadsheet. There's no formatting, worksheets, or anything fancy like that. So it's not strictly a competitor but it does the job.