This is a hard question to answer, here are the reasons why. One: we don't know what languages you know. Once we find that out then we can start to come up with some ideas for projects.
Second I don't know if you are understanding the meaning of Open Source. Once you right a program, have all the code ready to go then, you can decide how you want to copy right the material. There are a couple of license that you can use that will allow you to have your code be open source. One of the licenses is the GNU General Public License
. The other one is the Creative Commons License
. I would recommend that you do some reading on both and see which one would fit you best.
Lets start with that and then go from there.