Blogs

The Moz inbound marketing blog provides tips, tricks and advice for search, social and content marketing

Search Engine Land is the go to place for all information about search engine marketing and optimization

SEO by the Sea explores search engine patents and white papers

SEW covers all marketing topics like SEM, SEO, PPC & Social Media and much more

Search Engine Roundtable reports on the most interesting threads taking place at the various SEM forums

Marketing tips and ideas from Brian Dean

Marketing tips and ideas from Glen Allsopp

Some really great guides in here on topics like pagination.

Content marketing tools and training for online marketers and copywriters

These guys publish a lot of marketing related content, with a strong focus on social media