Opera, which is in my view one of the best web browsers, was formerly sold as adware; if you liked the program you registered, to stop the ads appearing in a little box at the top of the screen.
Apparently so many people have now registered that they are dropping this - from now on it's simply a free program. You can pay for "premium service", which is presumably technical support, but you don't have to.
I'm VERY pleased to see them taking this step - I have no idea if it's actually the right step for them to take, though given the existence of free programs like Firefox I don't think they had much alternative, but to me it's a vindication of the whole shareware principle. I'm not even going to bitch about having paid for it a few times, since that's the way shareware really ought to work.
Anyway, the latest version is at:
Later: Forgot to say that this is a new release that fixes some security issues, bugs, etc., not the same version that they were giving away on their tenth anniversary a few weeks ago. Also forgot to say that this applies to all operating systems, not just windows.