Present Perfect, Present Perfect Progressive, and Simple Past
Simple Past and Present Perfect - Monash University
Simple Past and Present Perfect: ELC Study Zone UVic - Introduction and five exercises
Simple Past and Present Perfect - ESL at About.Com
Present Perfect - Grammar Quizzes
Simple Past and Present Perfect - ELC Study Zone UVic
Perfect or Progressive - ESL at About.Com
Past Time Tutorial - Net Grammar
Present Perfect Progressive - Teacher Video Explanation