How to make money from freeware downloads.

I have done the ads on the download page and the rest of the site. I am making over 1000 a month from those.  I have submitted my application to hundreds of freeware download sites.  So most of my downloads come from these download sites where I cannot place the ads.    I get anywhere between 40,000 to 70,000 downloads a month.  So if I cold monetize this somehow it would be a good thing.     I put a donate button on there for a while.  I would occasionally get a dollar here and there.  The few dollars I made from this did not seem to justify the donate button eye sore on the app.  The idea of embedding ads directly on the app sounds good.  

Has anyone tried tapjoy for in app advertising?

We haven't used tapjoy, but if you're looking at offer companies we've used both Gambit and SuperRewards with reasonable success.

The thing to watch with offer companies is that many of the ads and offers are full on scams (e.g sign up for a monthly ringtone for $20/month on your mobile bill).  In order to use these companies and remain a good citizen you need to monitor the offers closely.  They usually give you tools to do just that, so you can remove offers you deem dubious.  They can monetize quite well, but it's a murky pool to dive into and if you don't keep an eye on them you will get calls from irate consumers.

Doug