Various stress-reduction or relaxation exercises and techniques are available these days in a number of places, online and otherwise; and at least a few of them make a passing reference to PTSD (though rarely combat trauma).
Relaxation at first may seem to be an impossible goal for those with combat trauma, because jumpiness and hypervigilance appear to be hallmarks of the experience that also have helped keep troops alive.
However, the continual wearing-down and weakening of the nervous system over years from adrenaline surges and frequent experiences of "fight or flight" shows just how important it is to develop greater familiarity and experience with relaxation exercises.
Like riding a bike, it's a much better (and more effective) idea to DO these things than just READ about them -- especially if you want to give yourself a chance to "feel" the effects in your own body, and "test" for yourself whether these techniques really "work." (And don't forget the caregivers, partners or spouses of those suffering from PTSD: They also carry around a fair amount of stress... )
The emerging field of Mind-Body Medicine (ironic since the idea of mind-body medicine is actually quite old) is full of techniques and tools for stress-reduction and relaxation. Yoga and meditation, among others, are known for their ability to reduce stress. But occasionally on the Web there's also a good guide for sufferers about how to relax and renew. Just such a "technique" guide exists here: The subject is "Relaxation and Relaxation Exercises," and the guide was produced at the Trauma Center, with the funding of the Massachusetts Office for Victim Assistance (MOVA), under a federal Anti-Terrorism Supplemental Grant (ATSG), to aid Victims of and Responders to the 9/11 Terrorist Attacks. Click here for a link to the guide online.
Also look on the left-hand column of this blog to see a number of resources in the form of books, CDs, and DVDs for stress-reduction and relaxation, including music designed to help people relax and de-stress. A section called "Healing Multimedia" is located about 3/4 of the way down the page (if you think of the blog as a single page, and just cursor down to that), or you could do a search (Cntrl F on most computers, or Apple F on Macs) for "healing multimedia" to find that section of recommended resources. Enjoy!