In Magic of Incarnum, there is a feat- Incarnum Reinforced Body or some such- that grants bonus HP for each Incarnum feat the PC has.
There is also an Incarnum feat that grants temporary HP equal to the amount of essentia infused into the feat, and (as I recall) another that lets you heal yourself.
Though not technically increasing HP, the Spellfire feat allows healing with absorbed magic, effectively resulting in more HP. The Spellfire Wielder PrCl increases the efficacy of that ability by improving the ability to absorb & store that magic.