This is the Powerpoint I use to teach my students the Imperfect Subjunctive. This Powerpoint assumes that they have already learned the Present Subjunctive. I use WEDDING for my Subjunctive triggers. Since this is a Powerpoint file it could be easily modified for the WEIRDOs out there. (a little Spanish teacher joke) :) There are 14 slides with 3 interactive ¡Practiquemos! slides to allow students to check their comprehension.
You can buy this ppt bundled with my other Subjunctive ppts. here: http://www.teacherspayteachers.com/Product/Subjunctive-Super-Bundle-1593887