Gnumeric

Gnumeric is a spreadsheet editor. Gnumeric is capable of reading and writing MS Excel (XLS and Office Open XML), and reading Lotus, Applix, Quattro Pro, OpenCalc (ODF), XBase, DIF, SYLK, HTML, Psion, MPS, oleo, sc, misc. text formats, and its native XML. It can also generate Latex, HTML, and others. A plugin system lets you extend Gnumeric, adding functions, I/O formats, and real time data capabilities. The existing Python, Guile, and Perl plugins let you define complex functions.