Now, the DADGAD-tuning, or open sus4 tuning as it is also called, is a very common tuning in both modern rock, and alternative pop. I guess for the mainstream audience it was brought to light during the grunge-era more than anything else, when bands where trying to find that "in between" sound, sounding minor without playing regular old minor chords.
These kind of tuning lends themselves very well to that "alternate rock sound", with the droning open strings. And they will give singers a good background from which to build melodies that transcend regular minor or minor structures. Listen to old Alice in Chains, or newer bands like Creed and Alter Bridge, and you will hear this tuning used in abundance.
The first example I've given here is just moving power chords around, and allowing the top string to ring out, creating that "neither major nor minor" sound. Cool stuff! This of course also works GREAT with distortion. :)
The second example is one that perhaps could be an intro to a more distorted riff. The fingerings, again, are very common place stuff, but the voicings they create are less so. Now with this particular example we are actually not doing anything different from what we would in a standard Drop-D tuning (perhaps the most common altered tuning in rock). However, try taking this fingering up to the next set of stringsor incorporating other open strings, and you will get some very cool sounding ideas!