Most Popular Data Mining Software
Surveys conducted by
KDD Nuggets 
and
Rexer Analytics 
have asked people involved in data mining what software they use. While it's not necessarily true that the most popular software is the best for a particular purpose, they can help guide you in choosing what software to evaluate. You can also see our
full list of data mining software.
Rexer Analytics Survey (Early 2007)
This survey asked about the tools which were used frequently and occasionally. Clearly more popular than the rest were the top 3 most frequently used:
- SPSS or SPSS Clementine
- "Own Code"
- SAS or SAS Enterprise Miner
Following on from these were
- R
- Weka
- C4.5 / C5.0 / See5
Rexer's analysis is quite in depth, and you can
obtain the 7 page summary report 
by contacting Rexer.
Rexer Analytics 2008 Survey
Rexer's 2008 survey is underway. Please enter the following access code
TDM08 when you
take part in the survey 
. This code helps Rexer analyse where people heard of the survey.
KDD Nuggets Survey (May 2007)
Top ten most used packages:
- SPSS/ SPSS Clementine
- Salford Systems CART/MARS/TreeNet/RF
- Yale (now Rapid Miner)
- SAS / SAS Enterprise Miner
- Angoss Knowledge Studio / Knowledge Seeker
- KXEN?
- Weka
- R
- Microsoft SQL Server?
- MATLAB?
Note: I've omitted Microsoft Excel from the list as it's not really "data mining" software, and I've merged the tools offered by a single vendor (SPSS and SAS)
You can
see the full survey results 
for more details.