What I've found is all you need is traffic to make money online, varying forms of traffic mind you. Most of the examples below deal with traffic from search engines and not referrals from other sites, but if you can find sites that give similar results to search engine traffic, all the better and please let me know lol, though they'd probably be niche specific.
Three kinds of traffic.
First is what I like to call "all traffic" this is all the traffic coming to your blog, if your blog is focused then "all traffic" is "targeted traffic" this would be greatly suited to contextual advertising like Adsense and because your blog is focused any traffic you get would likely be interested in much of the rest of your blog and the targeted ads displayed.
Second is the age old "targeted traffic" this is traffic that arrives at you blog because of your focus, a post you wrote or a specific topic. Targeted traffic works well with adsense on a site wide level, targeted traffic also works wonders on post level with affiliate and referral programs, for example if you write a post about a product e.g chewing gum and you have an affiliate link in there that sells chewing gum and the traffic you get to that post wants to buy chewing gum, then you've got yourself a winner. The thing is that traffic came because you targeted it and you did your research to make it happen.
Lastly for now is "long tail traffic" this is traffic that would come under "all traffic" but is not specific enough to be hugely "targeted traffic", it could work well with adsense but probably wouldn't be so great with affiliate and referral programs, mainly because you haven't targeted what they are looking for. The upside to this is if you notice a pattern in you long tale traffic you can write a targeted post concentrated on it and turn it into targeted traffic, adding in a few aff links or what not, if it suits it that is.
How would you go about getting these types of traffic?
All Traffic - You get this traffic as you keep on keeping on. Keep your blog focused and the rest will be a lot easier to achieve.
Targeted Traffic - Takes work, research and testing. Research your keywords, competition, get targeted backlinks to your posts and blog, then look into how you can monetize you efforts.
Long Tail Traffic - These are happy accidents in my opinion that you can turn into targeted traffic sources.
So there's three kinds of traffic that you can monetize, do it, increase it, repeat it and make more money online.