All of these are Free/Open Source Software, all run on Windows, Linux and Mac OS X. I’ve used them all, on some or all three of these operating systems. Follow the links to download; they are all free (but welcome donations).
Openoffice.org (yes, that’s the name) General office application, with a word processor, spreadsheet, presentations, drawing, mathematical equation editor, database.
LyX, a document processor, which is a WYSIWYM application (What You See Is What You Mean). Uses LaTeX in the background to typeset documents beautifully. Excels for long documents, or documents with many mathematical formulas. I am going to have my undergraduate students in the Mathematical Economics course use it for homework assignments this semester; I’m hoping that my assistant and I will not be too inundated with requests for help from the students.
More in a later post.