Check out these sites and blogs for great articles on copywriting, internet marketing, search engine optimization, and more.
Copyblogger is the granddaddy of ‘em all, with a fantastic blog and a ton of materials in the form of ebooks, seminar, webinars, and more. If you sign up you get access to a bunch of stuff, including their Copywriting 101 materials.
The Content Marketing Institute, like Copyblogger, also has a lot of resources, but its scope is wider. It covers writing, content marketing, content distribution, social media, list-building, and more.
KISSmetrics looks at internet marketing from the angle of analytics and testing.
Moz, which used to be SEO Moz, still focuses on SEO and all the things that go into improving website rankings. There’s a strong educational component on this site, which has courses like The Beginners Guide to SEO.
Remember that the “rules” for SEO are constantly changing, since they depend on search engine algorithms that are also constantly changing. For that reason, you might want to limit yourself to the last 3 months or 6 months (at the most) of posts and articles on SEO and SEM sites, otherwise you risk reading about techniques that are no longer optimal.
Any one of these sites could keep you busy for days, if not weeks, with the great content they have. Enjoy!