litmus paper- red and blue bromothymol blue- yellow in acid; clear in neutral; purple in base pH paper- universal indicator-range of colors cabbage juiceg
Phenolphtalein
Tamarind.* Litmus.* China Rose.* Turmeric.
Red Cabbage Juice can be used as an easy natural indicator.Bromothymol Blue is a common chemical pH indicator
1,10-Phenanthroline http://en.wikipedia.org/wiki/Redox_indicator should list quite a few.