I’ve started a contest on WritersCafe and even though I specifically asked for the entries to be polished and checked for spelling and grammar issues, some entries have ignored this. The correct usage of spelling and punctuation is such a basic requirement of writing, so here I’m going to collect some links to proper grammar and, if I find any, spelling.
How to use a semicolon – The Oatmeal
The 3 Most Common Uses of Irony – also The Oatmeal (I know this isn’t either spelling or grammar, but irony is commonly misused).
How to Punctuate Dialogue – This Business of Writing. PLEASE read this one. PLEASE, PLEASE, PLEASE.
Basic English Punctuation Rules – About.com: English as a Second Language. This really is a basic overview of punctuation use.
Rules of Apostrophe Usage – Suite101
How to Use the Apostrophe – Write101 (These two apostrophe usage articles are similar, but explained slightly differently)
I might add more as I come across them, but this should give you a basic grounding in the use of English punctuation.