QETools
- Six Sigma statistical tools (Excel Add-in) from basic descriptive stats and hypothesis testing to control charting, regression, ANOVA and more. Demo download. Purchase online.
- http://www.qetools.com

XLMiner
- XLMiner is a comprehensive data mining add-in for Excel, with neural nets, classification and regression trees, logistic regression, linear regression, clustering, principal components, and more. Trial version available, requires Excel 2000 or later
- http://www.resample.com/xlminer/index.shtml

Zumastat
- Provides ability to calculate confidence intervals for correlations, power analysis, and meta analysis (and many more) using summary statistics. Contains many advanced functions. Evaluation download not available, purchase online.
- http://www.zumastat.com

Microsoft Data Analysis Toolpak
- Free add in included with Excel but not enabled by default. Calculates many descriptive and inferential statistics.
- http://office.microsoft.com/en-us/assistance/HP052038731033.aspx

StatTools
- Advanced statistical analysis add-in for Microsoft Excel. StatTools replaces Excel's stats function with 36 robust statistical procedures.
- http://www.palisade.com/stattools/

EZAnalyze
- Free Excel Add In designed to permit the calculation of basic descriptive and inferential statistics without selecting ranges or typing formulas
- http://www.ezanalyze.com

Unistat Ltd.
- Makes and sells Unistat for Windows: comprehensive stand-alone statistical package that can also be an Excel add-in. A one stop solution for data handling, analysis, and presentation quality scientific graphics.
- http://www.unistat.com/

statistiXL
- Statistics add-in for Microsoft Excel. Includes univariate and multivariate tests such as ANOVA, Correlation, Regression, PCA, Factor and Discriminant Analysis.
- http://www.statistixl.com

WinSTAT
- An Excel Add-In providing statistical tests and diagrams. Demonstration download.
- http://www.winstat.com/

SigmaXL
- Pareto Pro is an add-in for Microsoft Excel 97, 2000 and XP, which allows you to create single and multiple charts. Performs analysis that will slice and dice data. Includes free demos and product list.
- http://www.sigmaxl.com/

XLSTAT
- Data analysis and statistics add-in for Excel. Includes over 40 statistical and data analysis features for statistics experts, researchers, students, and teachers. Buy on-line or download trial version.
- http://www.xlstat.com/

Analyse-It
- Statistical software integrated into Microsoft Excel for linear regression, anova, chi-square and other functions. Download evaluation.
- http://www.analyse-it.com/