The concept of search engine optimization isn't that difficult when you know what you are doing. I've been making money online using SEO techniques for around 10 years as an SEO consultant and the hard part isn't gaining traffic from search engines like Google, it's making money from that search engine traffic.
For example I have a jokes website that gets up to 10,000 unique visitors a day, on a good day I'll make $25 from the traffic, because I've not got around to fully monetising it yet!
If you currently do not own a site, don't have a lot of money, but want to go a little further than registering free Blogspot or WordPress blogs: not a bad way to make money, but much better to use them like I'm using this free blog to feed traffic and links to my important site. My advice is look at the self hosted version of WordPress, it's brilliant from an SEO perspective, especially with a little effort during the setup phase.
WordPress as a SEO CMS
WordPress is a blogging platform, but it's quite easy to turn it into a general SEO CMS. I've written a SEO Tutorial for WordPress
which explains how to use WordPress for maximum SEO results, on the same site I also sell WordPress SEO/AdSense themes, the best one by far is the Talian WordPress Theme
After you have a SEO'd site using WordPress as long as you always use relevant keywords for the title of new blog posts and scatter your keyword through the pages, you've gone a long way to gaining search engine traffic.
Take this page you are reading now, title:Making Money with Search Engine Optimization
It's got 5 relevant keywords. Look through the text within this article and you'll find those keywords and other related/relevant keywords scattered through out the text. It's not hard to do, just make sure you use the keywords and phrases you want to rank well for. don't worry about keyword density, if you can use a keyword or relevant phrase, use it.
That's the easy part, after that we have to find links to your site and then make money from the search engine traffic, but I'll leave those to another article :-)