Driving 3V chips from 3V3 chips and vice versa
I don't think that would be a problem - just make sure the 3V part's \$V_{OH}\$ is higher than the 3.3V part's \$V_{IH}\$ and the 3.3V part's \$V_{OL}\$ is lower than the 3V part's \$V_{IL}\$, and if you are really paranoid add a resistor on the line.