Merriam-Webster offers a Word of the Day that you can listen to online, or download as a free podcast. If you use iTunes, it’s available there, too. In either form you can read the text and listen to it at the same time—a big help if you’re not sure how to pronounce the word. Recommended!
And of course if you have an iPod or something like it you can listen to the word of the day while you’re on the school bus—a painless way to improve your vocabulary. Put your iPod in shuffle mode, and you’ve got built-in review. Brilliant.