GeoMerge

GeoMerge is an application you can use to merge multiple maps into a single file. It offers support for ESRI Shapefiles and MapInfo TAB file extensions. The tool includes intuitive options that can be tackled even by users with no previous experience in map software.

Simple installer and interface

The setup operation is a fast task that shouldn't give you any trouble, thanks to the fact that there aren't any special options, prerequisite software products, or third-party components involved.
As far as the interface is concerned, the program adopts a large window with a plain appearance and layout, where you can use the built-in tree view to navigate disk directories and locate SHP or TAB files.

Combine ESRI Shapefiles and MapInfo TAB files into SHP

GeoMerge shows all files from any selected directory which match one of the two file types. It cannot show both SHP and TAB-formatted files at the same time, though.
On the other hand, you can populate a task list with multiple files with the same or different formats and from different folders before proceeding with the merger. Just keep in mind that that the items must have the same shape types (column definitions). Otherwise, you will encounter an error.
You can specify the output directory to combine the files into one SHP item while keeping in mind that any TAB files will be automatically converted to this format. Afterward, you can open the new file to inspect results. Apart from the fact that you can remove an entry from the list if you change your mind or clear everything to start the task from scratch, there are no other notable options available.

Evaluation and conclusion

We haven't experienced any stability issues in our tests, since it didn't hang, crash or prompt error messages. Tasks were carried out fast while CPU and RAM usage was minimal.
To sum it up, GeoMerge may not have a particularly rich set of features, but it offers a straightforward solution for combining multiple SHP and TAB files into a single SHP map file. It's free.