BUGS project (Winbugs)
http://www.mrc-bsu.cam.ac.uk/bugs/winbugs/contents.shtml
ClusterSeer
http://www.terraseer.com/products/clusterseer.html
Epi-Info
http://www.epiinfo.it/
Episheet
http://members.aol.com/krothman/modepi.htm
GeoSurveillance
http://www.acsu.buffalo.edu/~rogerson/geosurv.htm
NCSS - Statistical & Power Analysis Software
http://www.ncss.com/
PS: Power and sample size calculation
http://biostat.mc.vanderbilt.edu/twiki/bin/view/Main/PowerSampleSize
Power V3.0
http://dceg.cancer.gov/bb/tools/power
R
http://www.r-project.org/
SAS
www.sas.com
SaTScan™
http://www.satscan.org/
SPSS
www.spss.com
STATA
www.stata.com
Sampsize
http://sampsize.sourceforge.net/
Splus
http://www.insightful.com/products/splus/default.asp