What are the best ways to monetize a web based service that is free, other than ads?

You can: - Sell Enterprise dedicated instances - Sell microtransactions and subscriptions (charge for certain features or transactions) - Sell services around your platform - Sell user data (not their contact info or anything identifiable, unless it's the type of business you want to do) - Ask for donations - Sponsored content - Affiliate links, so you don't "advertise", you "refer" - Set a limit on the free tier, a limit at which you feel uncomfortable losing money - Do consulting using your platform to perform your work

How about partnering to bundle the service with a complementary item that's of value and charging the bundle owner (i.e. licensing your service with a bundle). Worked for Microsoft :)

Sell product or service on subscription basis.

I'd think about using the service you have created to prove that you can perform a task and then sell that task. I'm guessing that is what @caroline_chiari1 is referring to. It is a similar approach that home builders use for model homes.