What is better than HN itself. Post your idea here and check for feedback. This is what i have personally done. I keep track of my ideas in my blog and post them here on HN. If people read it and think it has some potential, they will respond back to it. And it could be your lucky day, and PG himself will give u some inputs (kind of like limited version of virtual office hrs). I do share my ideas with my friends too as some time they give the best of the advice.