Sites providing information and instruction on grammar issues

• English Grammar Aids for Both Native Speakers and Students. The New York Times 
• 15 Tips and Tools for Teaching Grammar
• Resources for teaching grammar from The Guardian
• Peter Smagorinsky: Resources on grammar instruction 
• Troy Hicks: Using Technology to Teacher Sentence Combining
• Guide to Ambiguous Grammar: Provides interactive examples of shifts to passive to obscure subject action
• Murphy's English Grammar in Use 
• Analyzing Writing using FoxType to determine grammar and "politeness" 
• NoRedInk  
• Grammarly 
• Grammar App 
• GrammarBook  
• Grammar Girl  
• GrammarUp 
• English Grammar Book
• Sentence Tree: Type in a sentence to perceive a map of that sentence based on syntactical components 

Grammar and Spelling Checkers

•  After the Deadline 
• Grammerly 
• Editminion 
• ProWritingAid
• Spellchecker
• GNU Aspell
• Hunspell
• KeySpell
• Ispell
• MySpell
• Pspell
• TextTrust.com
• JSpell HTML
• AsPeopleSay
• Grammar Slammer
• Whitesmoke
• Grammar Sentence Checker
• Stylewriter
• Language Tool
• Link Grammar Parser
• Grammar Now
• Grammar Check

iOS spelling check apps 

• Speller 
• Spell Better 
• Spell Check 
• Miss Spell’s Class 

Android spelling and grammar check apps 

• Spell Checker Editor 
• Spell Checker 
• Spell Check and Grammar Keyboard 
• Miss Spell’s Class