We run a website with esl resources, mainly esl lesson plans:
www.english-4u.com. We base our lesson plans on current news stories
and lyrics of popular songs. We want to know precisely what topics esl
teachers and their students are interested in, so we can provide them
with esl lessons they expect.

I applaud your interest in determining what topics ESL teachers would
want to have as lesson plans.

AS you know, each teaching situation is different with differing
goals, different aged students, different expectations.

Why not have as part of the registration process for your site an
opportunity for them to list topics they are interested in teaching?
You might also give them a list you have generated and have them rank
order it.

Perhaps one day you'll have a site for EFL teachers, too.

Best of luck!