I just repaired one on an old Ben Pearson of my uncles, I took some five minute epoxy (it's flexable enough not to break) and filled the crack/splinter, then smoothed it over to even out the surface of the bow.
After doing this, I applied some "Skin Eez" bow covering to the back...look up their web site, it's pretty cool, can make an old beat up bow look really nice.
I've been shooting the bow some, checking the split periodically, and have had no problems with it. This is the first time I've done something like this before, so I'd check around with some more of the more knowlegable fellows before doing it.