I wonder, is there any reason to not make "power cards" for your trained skills? They are typically at-will standard actions (though some are not standard actions), there are rules for what you can do with them and the general DCs you need to hit, they increase with level, they pretty much fit most of the pattern for all other powers.
I think if my Ranger had at-will power cards for "Twin Strike", "Nimble Strike", "Acrobatic Stunt", "Athletic Movement", and "Sneaky Movement" I would be more inclined to use Acrobatics, Athletics, and Sneak than I am right now.
Similarly, the character with a lot of trained charisma skills might have a "Communication" card, and the guy with the knowledge skills might have a "Knowledge" card.
Providing "power cards" for activities you can already technically do but which is normally on a part of your character sheet that is not often referenced during encounters is likely to encourage those activities.