Here are some of my favorite meditations from Beliefnet. I use these whenever I'm feeling anxious or stressed.

Mindfulness Meditation: "A Moment of Calm" by Tara Brach
http://www.beliefnet.com/story/3/story_385_1.html

"A Breathing Exercise" and "Calm Waters," both by Thich Nhat Hanh
http://www.beliefnet.com/story/43/story_4371_1.html

Opening the Heart, by Sharon Salzberg
http://www.beliefnet.com/story/32/story_3248_1.html