Grammar is the system and structure of linguistics and includes morphology, structure, and semantics.
Regular Blogs
The subtitle of this weblog is "Mocking Poor Grammar since 2007," and it displays grammar violations from all kinds of sources, and specializes in apostrophe abuse, spelling, punctuation, and typos.
http://www.grammarblog.co.uk/
Contains sections about grammar, punctuation, word choices, and style. It digs into where particulars came from, such as the "at" symbol, and when to use single versus double quotation marks.
http://grammar.quickanddirtytips.com/
Delves into grammar rules and points out those which are, in the blogger's opinion, bad rules and explains why.
http://motivatedgrammar.wordpress.com/
Comprehensive blog about learning languages, studying or working abroad that is full of tips, tricks and guides. Our knowledge is for everyone and for free!
http://speaklikenative.com/
Maintained by an English major and freelance editor, this weblog is about bad spelling, inaccurate punctuation, and misplaced apostrophes.
http://thegrammarvandal.wordpress.com/