Infolinks is probably the highest paying option for your in-text advertising. On DLM, you will see underlined links scattered throughout articles. Those are a function of Infolinks and without disclosing too much, it's been a great source of income. Best is that they accept all sizes of websites and blogs. Just sign up and begin.
This is a simple store development platform which enables you to create content based sites that generate income through the eBay affiliate programs. Pretty darn simple and increasingly popular.
Start a blog and consistently write excellent content. With good ad placement, you may make some money. I detail my process here: Simply Said, How to Blog.
Their eMiniMalls service has shown great results for many Bloggers and site owners. You choose a keyword and they show relevant products on your site using a pretty unique interface.
If you have a site, you can join Commission Junction. Once enrolled for free, you can choose companies whose ads are pertinent to your site. Companies have the ultimate say on working with you. There are easily over 1,000 companies to choose from here.
For blogs only, advertisers provide you with a topic and you write about it on your site. To do this, you have to install a flash widget into your blog post. The more people you bring into the conversation through the widget, the more you get paid. It's difficult to explain.
If you are an expert on something, Ether provides a way for people to pay you to talk about it in a one-on-one setting. If you want to charge $250/hr, that's fine. You have to do all the advertising so you should have a blog or site already established.
This is an arm of Text Link Ads and is currently only good for Wordpress users. This does me no good currently, but as you can guess, they place ads in your feed(s).
Not only are they the best place to house your feeds, they will also add ads to your feed and website. You get paid per impression and if you implement Google Adsense to your feed, you are paid per click.
Create simple text ads and choose keywords that determine when they are displayed. This is where the Adsense Content comes from. You do not need a site for this.
Get paid to fill jobs. Commissions range from $50-$5,000. It all depends on how tough the job is to fill and how desperate the hiring company is. This is another one that's tough to explain.
Add their job board to your site. They then post jobs based on the geographic location of visitors and the position types you pre-select. I tried it and I they continually report that I sent 0 visitors and I know that's not right. Nevertheless, I may have an isolated problem so they make the list.
It's a pretty flaky model but if you have a Rolodex full of good contacts, you can sell them here. I can't make sense of it but it looks like you get $0.10 per profile.
If you have a site, you can join Linkshare. Once enrolled for free, you can choose companies whose ads are pertinent to your site. Companies have the ultimate say on working with you. Like Commission Junction, there are a ton of companies waiting to evaluate your site.
If you have an RSS feed, run it through Pheedo. Like Feedburner, they can include ads into your feed and if you really become large, advertisers will pay a premium for you to show their ads.
I've used them for a couple years for some banner advertising. They are similar to Commission Junction and Linkshare however they seem to have lower tiered companies with advertising offers.
I have never made a dime here but I know people that have. You can earn by sending advertisers to them or by selling spots on your site. You must have a real site or blog to do this - nothing on a shared domain (i.e. /blogspot).
Don't bother unless your site has 500,000 page views of text based content a month. If you have that readership, these are the guys that display bubble box ads to underlined words on your site.
Not entirely online but this is worth a mention because it's won awards and is very legitimate. If you are an at-home Mom or free-lancer without work, you should check this out.