Are there any specific CRA rules for giving/lending or being involvoed with habitat for humanity?

Time served by employees off the clock does count for service hours.
You could donate to the Habitat and that would count given you show that the money went to low-moderate income families.
Lending to them would probably count as well.

dittos on Rizzy!

You could get service credit if you served on the board or a committee using your banking expertise, but not for swinging hammers.

Most Habitats only accept families with incomes less than 60% of MFI for the area, so the investments and loans are slam dunks.