How to market a web application for entrepreneurs and small businesses?

[Mike]

I have created a web based application that has a calendar, appointment page, clients page, services and products page, email sending page, notes, users, promotions page and so on... it has really become a huge software. My gf who is a wedding photographer and an entrepreneur is using it and has more than 100 clients in it, so the software has proved that it actually works in real business. (of course small size business)

Now I am thinking how I can actually market this. Either by selling the whole site to a software company or selling memberships for entrepreneurs.

I am not sure how to do this part.

Any ideas will be appreciated