List of business app stores / market places?

Hi there,

This is my first post here, but I'm a big fan of the podcast and a boostrapper at heart.

I've had some success building an app the Shopify app store. It's been great because the app store acts as a natural acquisition channel.

Now, I'm looking for an idea for my next app.

Could you suggest other popular business app stores?

Other ones I can think of are Xero, QuickBooks and SalesForce, but I'm wondering if I'm missing other good ones?

Thanks!

Clement

ps: it doesn't matter if they are crowded app stores with lots of apps. Actually, I see that as a good thing.