Here are the 5 blogs that I visit regularly, in alphabetical order:
Aaron Wall’s SEO Book
This blog is focused on the search engines and the SEO world. Aaron usually makes some pretty good points.
Danny Sullivan’s Blog
Danny’s personal blog, where he talks about search engines as well as anything that comes to his mind.
Jensense – Making Sense of Contextual Advertising
This is a must read for anyone involved in Adsense, YPN, or any other similar programs. Jennifer Slegg talks about major happenings with these types of programs. Sometimes I find out about these changes through this site first!
Search Engine Watch
Search Engine Watch has a wealth of information on what’s going on in the search engine world. One nice feature I like is the “Search Engine Forums Spotlight”, where it lists the topics of interest from the various search engine forums.
SEO Black Hat by QuadsZilla
This blog talks about some of the more, shall we say, “interesting”, ways of doing SEO (it’s called SEO Black Hat for a reason, right?) You may or may not agree with some of the techniques discussed there, but it’s always good to know what others are doing.