There's something Dale Carnegie conceptualized in his book "How to Win Friends and Influence People" that fits very well here:
If you would like to ignite interest and motivation in a person think from their perspective, and when you speak to them speak on terms that resonate with them.
Think from the perspective of a random internet stranger who comes across your internet post. What about it would cause a genuine interest in teaming up with you? Talk about things that would benefit them! If you don't have much experience talk about the good feelings that result from teaching someone something (there is a reason people respond to questions on this forum, and it's not money), if you have a lot of experience talk about the benefits of multiple minds working toward a common goal.
There is a symbiosis out there waiting for you to unlock- you just have to coax it out with gentle persuasion, and a bit of persistence.
I've been writing an OS. Just got it into 32bit protected mode, pretty much ready for higher language linkage. Would be a fun project to "Teach C++ from the ground up: From metal to machine".
I also think that sounds like a good idea, but I wouldn't have any ideas on what we could do...
Most of the time :)
We are mostly a kind of "give us a shout if you've got a problem, and we'll see if someone can help... If not we'll just have fun and chat"
But if you ask there are plenty of people that I'm sure would be happy to work in projects... A couple of people are always on project eula because they don't know what to do :)