I found a source of Guided Mindfulness Meditation at UCLA. And best of all, the meditations (7 for PC, 15 for iTunes) are free. If you have an iPod, iPhone, iPad you can download them from iTunes. If you are using a PC, you will select to play the meditation on your computer. Bookmark the web page so that you can easily get back to it.
Remember, 15-20 minutes of Mindfulness Meditation a day increases attention skills in teenagers and adults with ADHD by 30% - with or without meds. And by the way, this is 30% over and above the effect they are getting from meds if they are on them. Meditation also decreases anxiety and makes people happier :)
If you want to learn more on the topic, there are two lectures on the UCLA site including a Ted lecture on Mindfulness Meditation by Diana Winston.