Here are two no-BS, straight forward guided meditations by Sam Harris, one is 9 and another 26 minutes long.

http://www.samharris.org/blog/item/mindfulness-meditation

Here is a bit more background on it: http://www.samharris.org/blog/item/how-to-meditate

There is plenty of scientifically backed studies and documents out there when it comes to mindfulness If you are a skeptic though, as am I, be wary of the masses of esoterically/religiously contaminated resources on the web, when it comes to meditation.