To me, it sounds like web programming fits the bill of the type of skill that you say you want. The only question is whether it will be worth the effort to get through the learning curve (though you can basically get started doing stuff very fast), and dealing the frustration of problems that take time to solve.

I really have no idea how well the benefits and costs will match up to other things you can spend your time on, but it does seem that web programming skills could be an asset for your effort in the domains of nootropics and existential risk reduction. Here are a few random ideas that web programming could help you implement:

• Making a blog for some x-risk entity, or running your own x-risk blog, or any kind of outreach website
• Making a database of information on nootropics with a web interface (even just for yourself, or people working with you; there is plenty use for websites or web services that don't face the public)
• Making a website where people can journal or share information on nootropics ("NooBook?")

Every cause wants to be a cult... and also have a sweet website.