Hendricks-McAfee Bilateral Oligopoly Model
Here is a mathematica program to compute the effects of mergers, and computes all the statistics. In addition, there is an excel spreadsheet that lets you compute the MHI and other statistics based on market share and other data. Note that the excel spreadsheet requires using Excel's solver to compute the solution. It is not yet fully documented, although it should be reasonably clear as it has an example built-in.