What can I do to increase revenue?

Good idea. A little feedback on my user experience, when i created an account with the name "tom" i thought i was going to get an email, went back a minute later and saw the an error message saying my name must be between 3 and whatever characters. I re-did it, even though "tom" is 3 characters, and haven't gotten an email yet, it's been a few minutes, and its not in a spam folder. I think you may be causing some people to turn away at the door by making it take longer than necessary to login to the site. Maybe just let them create their own password if it will save time for the end user to login.

Also, not being logged in, I dont see any kind of call to action. Trying to look deeper, i realized there is content below the fold. The facebook widget going to your page takes up a lot of valuable space above the fold.

Once i got logged in, and ran a search with the drop-down item for premium, it told me to sign up for the plan, but i can't find any way to sign up for it.

After looking around a while I realized that the premium account link was there, but below the fold and didn't really stand out to me at all.

My advice:

-Have a call to action above the fold. Make it pretty, draw focus to it.

-Make user account creation easier

-Make upgrading easier

-Run some google ads, do some a/b testing