Showing appreciation is important, but it's more meaningful if it's specific, timely, and sincere. "Nice job" is positive but not particularly meaningful. I once wrote a brief note of appreciation to a colleague and noticed it was still displayed at her usually spotless desk weeks later. I had no idea it would mean that much to her. You don't need to be a manager to show appreciation.

p.s. Silverofx: It's Jeff Moden, not Jeff Morden