What are some good subreddits to share your website?

So this year I took up a challenge to study what makes a product go viral, and document the lessons on my blog.

My plan is to launch micro-products (things that cost less than $100 to outsource) to see what gains traction, and why one fails or succeeds.

Towards this, I launched my first product late last month - QuickXLS, a simple tool to share spreadsheets online.

Now, I have two challenges:

1. Finding the right place to share this product
2. Finding the right use-cases for this product

I introduced this on the InternetIsBeautiful sub and got a handful of visitors. I was hoping to get some ideas on the product -market fit through this, but I am still where I was.

Are there other subreddits where one can share their websites? I need some real-life use of this app to figure who I should target this at.