This got me thinking so I've been Googling for a bit:
A lot of the sites are for 'rad tricks and sh*t' which is not my bag, but there a a few tidbits. Some are kind of obvious and I can't find much more. What's the name of that mag?...
http://www.nationalgeographic.com/adven ... ps_30.html
http://www.ehow.com/how_13779_fall-mountain-bike.html\
http://www.ehow.com/tips_13779.html
...Though unless you practice these techniques on giant mattresses, aren't you gonna break something before you train your body instinctively? You're not going to have time to make a decision when you're going down, so it has to be 'programmed' in.
I'm lucky only to have had one broken collarbone from yonks back but I lost 2" off my left shoulder because I wouldn't let them re-break an over-lapping clavicle. Fool am I! "Regrets, I've had a few".
The most common break is of course the collar bone/clavicle because when placing the arm out to break the fall that bone proportionaly absorbs the most energy versus it's strength. The arm often stays ridged (unless the wrist buckles, hence a wrist/arm break) automatically, telescoping the arm into the shoulder socket and crushing or bending the clavicle beyond it's means. Hence, to cut a long story short, the best advice is probably to fall 'curled up'. Easier said than done.
I feel for you Paul, it drives me nuts staring at the bike for weeks, feeling the fitness dwindle. Hope you have turbo trainer or a gym with decent bikes?...What fun!