Hey suppenthusiast, I thought I might actually contribute something to T-Nation for once..thanks for asking a question I can actually answer! Sorry for the irresponsible post but I don't have a link for you atm..when I get more time I'll post one for ya.
ALC (or ALCAR) and ALA were investigated by Dr. Bruce Ames for their effects an aging. ALC was used to boost functioning of cell mitochondria. The degredation of which was thought to be a major contributing factor to the aging process..or one of the things most notably affected.
This comes back to the "oxidative stress" idea of aging. There are those who theorize the aging process is primarily caused by the accumulation of oxidative damage with aging. While I think this is about as likely as finding a mystical spring with water that grants eternal youth, it is an essential piece of the aging puzzle.
As we age, our functioning declines even at the cellular level... and so Ames decided to test what effect increasing function of the mitochondria (the powerhouse of the cells) would have on lifespan. ALC was used to improve the functioning..which worked and did extend life span in lab rats (at least until a later study may or may not disprove that one, as studies often tend to do). But Ames further sought to combat the oxidative stress that comes along with aging, which may actually be increased with more metabolic activity with ALC. He used ALA for this task and together they seemed an ideal combo. ALA is an extremely potent antioxidant that is both water and fat soluble (an important quality) and can even (in a sense) recycle other antioxidants in the body. Bodybuilding use ALA for entirely different reasons I suspect. It has insulin-mimicking properties and is reputed to help provide quick bursts of energy for intense exercise.
ALC is also noted to increase acetylcholine levels in the brain to help combat mental decline with aging.
Acetyl-L-Carnitine Arginate is a new compound of ALC and Arginine combined. It's supposed to synergize the effects of ALC and Arginine (i.e. increased NO production) making it more effective than either one taken seperately. It was patented by Sigma-tau. I have no idea how much research has really been done on this substance or how reliable it might be.
Sorry for the rambling, un-succinct post but I hope I answered your question.