Feist - "The Reminder" is quite pleasant, but holds your interest too.
Then again, I'm not sure "chilled out" music actually works to de-stress people. If you're stressed, you probably build lot of pent up angst too so you need to burn that off sometimes. Chill out music is often too background to grab your attention and forget out about your worries. Something light and fun can work wonders, like The Pipettes album or this:
It's silly, but it'll make you smile
What de-stresses people depends very much on the individual. Bpitch Control style techno tends to do it for me, even though it has relatively high BPM. (double click on the tracks in the player below, doesn't work in all browsers)