[mabelkitty]

Example - I would buy a book or attend a seminar to learn about taking advantage of open source and Linux.

Sounds like a good niche to me.

Advertise "Free Software for your computer" then list all the tasks one could do with the free software.

[Abcdefg]

Bingo!
MySQL is free, yet I see lots of books on how to use it are selling at B&N. Even though there is documentation at the download site.