I'd go for a few modules which make the most sense to a typical computer user/programmer performing typical computer tasks. That way, there's the largest chance that they might actually use python on their own time.
In my opinion, the operations most people will likely perform are file operations, for example going over every file in a directory and performing some action on it.
Therefore, I'd say the modules: os and os.path are probably the most important, and also mention glob, fnmatch and shutil. Also, subprocess might be very useful too, since it tends to get used in the above mentioned context.
Lastly, I'd go with optparse, since that will get them into very quickly making usable, programmer-friendly programs, which hopefully will also encourage them to actually write programs that other people want to use.