Modules that extend Igor and software products that use Igor:
DataAccess allows Igor Pro to read electrophysiology files: Axon Instruments ABF and ATF, CED SON (Spike2) HEKA Patch and PatchMaster, and Bruxton Acquire.
SIDX allows Igor Pro to control scientific CCD cameras: Princeton Instruments, Photometrics, PCO/Cooke, Andor, SciMeasure, Spectral Instruments, DVC and Hammamatsu.
Iolite is Igor-based software for laser ablation ICPMS (inductively-coupled plasma mass spectroscopy).
Developer of the ABF Utility program that converts Igor Pro binary data files to Axon binary format.
SoftZymics produces data analysis software for enzymologists, including the package VisualEnzymics for the analysis of steady-state rate data.
Not strictly an add-on module, but Visual Integrity makes software to batch convert PS/EPS files to other formats such as XML-standard SVG, FrameMaker MIF and soon also PDF. See the PDF FLY page for more info.