This question is similar in intent to How do you help players not focus on the rules?, but more focused on a particular feature of D&D 4E: the power list. On today's Rule of Three's article, Rodney Thompson states:
The execution of the powers system in 4E also has an interesting psychological effect. Given the high number of powers each character has (even at 1st level, a character can have eight or more powers), they create a sort of tunnel vision for many players that makes it harder to improvise actions on the fly.
I've noticed this too, comparing the D&D 2E group I played in to the 4E group I usually DM. How do you make your players notice that they can actually do stuff on their own, without having to always rely on their powercards only?
I've tried giving them a brief on the use of skills (almost word-by-word from the Rules Compendium), but it hasn't worked for most of them (the player of our halfling thief is a notable exception).