I really like this idea but I think your categories are confused and confusing. First, I was disappointed to see the lack of a 'design' option. Then I wondered

I really like this idea but I think your categories are confused and confusing. First, I was disappointed to see the lack of a 'design' option. Then I wondered whether you could be a designer or a code mentor for each category. But designing for Ruby isn't really different to designing for Python (unless you're designing a framework etc). HTML/CSS is not design it's coding. Designing for HTML/CSS is certainly a technical design skill. Similarly iOS & Android present distinct design challenges despite both being 'mobile'. I'd be happy to advise on iOS design but would feel uncomfortable in advising on Android as I'm unsure about the native idioms. Could I suggest you add design categories for Visual design, Web design, UI/UX design, iOS design, Android design. You might want to consider copywriting too as it's a tricky and often overlooked part of the creative process (and something that certain YC alumni are naturally very good at).