Grammar Nouns and Verbs

Singular- plural:
http://www.english-room.com/3_plural.htm

http://www.english-room.com/plural_02.htm

Verb Ing-form  What are you doing?
http://www.eflnet.com/grammar/bgtverbagreement.php
http://www.carmenlu.com/first/grammar/begoingto1_2.htm

http://www.juntadeandalucia.es/averroes/torredelprado/ingles/presentcont1.htm

http://www.englishexercises.org/makeagame/viewgame.asp?id=983

http://esl.fis.edu/vocab/q21/doing2_r.htm