In second episode, Susan looks at the note used to blackmail Mary Alice and we can see that it has been folded twice and become somewhat crumpled. Two episodes later, in this episode, when the girls show the note to Paul, it is almost perfectly smooth with a single horizontal crease.
During Lynette and Gabrielle's conversation with Paul, Gabrielle is holding two boxes of chocolate. At first the cover of the boxes are facing outward, but in the next shot the back of the boxes are facing out, later they switch sides a couple more times.
When Susan and Mrs.Huber are together in the Supermarket the position of the egg box keeps changing in between shots on the conveyor belt.
When Andrew is talking to his mum, Bree, on his bed, we see him put the magazine down, yet in a later shot it is no longer there.
When Lynette is at the school, the teacher is waiting outside eating. If you look at her hands, you can see that she has a white napkin. The napkin changes from one hand to the other between shots, and in one shot it is small and the other it is not.
About 10 minutes in when Gabby is in the tub with Jon, when they heard the doorbell and he gets out of the tub very quickly, you can see that he is wearing underwear...he of course would not be wearing underwear normally.
When Bree is in the supermarket, as you see her place her two items, a carton of OJ and a carton of eggs, listen closely. The items are empty.