The standard save DC calculation is 10 +
1/2 Hit Dice + Ability Mod.
EDIT: For a spell or spell-like ability, however, it's based on the spell level. So, there wouldn't be any change. I missed your qualifiers on my first pass - mi excusa.
For an aboleth, for instance:
SRD said:
Psionics (Sp): At will—hypnotic pattern (DC 15), illusory wall (DC 17), mirage arcana (DC 18), persistent image (DC 18), programmed image (DC 19), project image (DC 20), veil (DC 19). Effective caster level 16th. The save DCs are Charisma-based.
Note that the aboleth has a normal Charisma score of 17 (+3).
The spell-like ability save DCs are thus:
1. Hypnotic pattern (DC 15): 10 + 2 + 3
2. Illusory wall (DC 17): 10 + 4 + 3
3. Mirage arcana (DC 18): 10 + 5 + 3
4. Persistent image (DC 18): 10 + 5 + 3
5. Programmed image (DC 19): 10 + 6 + 3
6. Project image (DC 20): 10 + 7 + 3
7. Veil (DC 19): 10 + 6 + 3
So, they follow the same progression with Hit Dice that normal spells do - none.