There are many open-source or free software projects that are likely to be of interest to sigTOOL users. A few are listed below:
Neural Modeling PyNN http://pynn.gforge.inria.fr/ neuroConstruct http://www.neuroconstruct.org/ Spike Processing FIND Toolbox http://find.bccn.uni-freiburg.de/ STA Toolkit http://neuroanalysis.org/wiki/doku.php/welcome NeuroSpec http://www.neurospec.org/ Image Analysis ImageJ http://rsbweb.nih.gov/ij/ Fiji http://pacific.mpi-cbg.de/wiki/index.php/Main_Page Ion channel analysis DCProgs http://www.ucl.ac.uk/Pharmacology/dcpr95.html EEG EEGLAB http://sccn.ucsd.edu/eeglab/ FieldTrip http://fieldtrip.fcdonders.nl/ EMG EMGLAB http://www.emglab.net/emglab/index.php Graphics JFreeChart http://www.jfree.org/jfreechart/ JZY3D http://code.google.com/p/jzy3d/ Mathematics Sage http://www.sagemath.org/
For a more extensive list, visit the INCF Software Page