Unconscious creatures get to make saving throws as normal, with the exception of having a -5 Dex modifier. From the Condition listing:
Unconscious: Unconscious creatures are knocked out and helpless. Unconsciousness can result from having negative hit points (but not more than the creature's Constitution score), or from nonlethal damage in excess of current hit points.
and further from helpless:
Helpless: A helpless character is paralyzed, held, bound, sleeping, unconscious, or otherwise completely at an opponent's mercy. A helpless target is treated as having a Dexterity of 0 (–5 modifier). Melee attacks against a helpless target get a +4 bonus (equivalent to attacking a prone target). Ranged attacks get no special bonus against helpless targets. Rogues can sneak attack helpless targets.
[Helpless creatures are subject to coup-de-grace]
Nothing here limits the availability of saving throws. Neither do the descriptions of the Saving Throws themselves:
Fortitude: These saves measure your ability to stand up to physical punishment or attacks against your vitality and health. Apply your Constitution modifier to your Fortitude saving throws.
Reflex: These saves test your ability to dodge area attacks and unexpected situations. Apply your Dexterity modifier to your Reflex saving throws.
Will: These saves reflect your resistance to mental influence as well as many magical effects. Apply your Wisdom modifier to your Will saving throws.
In absence of primary rules forbidding saving throws to unconscious creatures, they aren't.