MIF2Go 4.0—add-on for FrameMaker for $295 although it is free software "for anyone who is unemployed, is an underemployed consultant (you decide if you are), or is an academic, including students, faculty, and staff. It is also available to most nonprofits that work for humanitarian and ecological causes, and to groups that develop FOSS (Free Open Source Software). We do not require verification; we use the Honor System instead."
CINDEX—indexing tool for professional indexers
emDEX—indexing plug-in for FrameMaker
Index Assistant—index plug-in for Word (only $10)
IXgen—indexing plug-ins for FrameMaker and Word