Grammar (British Council)

This page is very useful to practice your grammar:
http://learnenglish.britishcouncil.org/en/grammar-exercises

Let's start with Countable & Uncountable nouns.
http://learnenglish.britishcouncil.org/en/grammar-exercises/countable-uncountable-nouns-1

Irregular verbs
http://learnenglish.britishcouncil.org/en/english-grammar/verbs/irregular-verbs

Sentences
http://www.bbc.co.uk/schools/starship/english/penguinsonice.shtml

Past simple and pas continuous
http://learnenglish.britishcouncil.org/en/grammar-exercises/past-continuous-and-past-simple