One option Joel doesn't mention is to use OpenOffice. It has its own object model (called UNO), which has bindings in many languages. It's not a perfect implem

One option Joel doesn't mention is to use OpenOffice. It has its own object model (called UNO), which has bindings in many languages. It's not a perfect implementation of the formats, but it's good enough for most things. And has the rather large advantage that you can run it under your favorite *nix.