Discussions About Learning English

Antimoon publishes an archive of an old forum on learning English. 
Look at this one about the difference betwee "outside" and "outside of".  
My favorite contribution is Foxie's: 
Besides meaning 'outside', in colloquial English 'outside of' can mean 'except for'. My favorite 'outside of' saying is "Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read."


Check out their tips on How to Learn English