Here are some links to free guided meditations from:
The UCLA Mindful Awareness Research Centre, there are different lengths depending on how much time you have – the idea with meditation is that it's more important to do it regularly – rather than to meditate for long periods of time and then not meditate again for a long time.
A Youtube link which takes you to a lot of meditations by the great Vietnamese Buddhist Monk Thich Nhat Hanh
Another very good teacher is Jon Kabat Zinn
Miriam Rose Ungunmerr Baumann speaking about Dadirri.
Book list on Mindfulness:
Mindfulness: Finding Peace in a Frantic World By Mark Williams and Danny Penman
Full Catastrophe Living by Jon Kabat-Zinn
The Emotional Life of Your Brain by Dr Richard Davidson
The Mindful Brain by Daniel Siegel
Peace is Every Step: The Path of Mindfulness in Everyday Life by Thich Nhat Hanh
Search Inside Yourself by Chade-Meng Tan