Publish or Perish is a software program that retrieves and analyzes academic citations. It uses Google Scholar and Microsoft Academic Search to obtain the raw citations, then analyzes these and presents impact metrics including H-index and others.
Please note: You should take care when using this software because Google Scholar citations are not always from scholarly journals or books. Publish or Perish allows you to screen these out and recalculate so your numbers are not inappropriately inflated.
The G-index aims to improve on the H-index by giving more weight to highly-cited articles. See Leo Egghe, Theory and practice of the g-index, Scientometrics, Vol. 69, No 1 (2006), pp. 131-152.
The E-index is the (square root) of the surplus of citations in the h-set beyond h2, i.e., beyond the theoretical minimum required to obtain a h-index of 'h'. The aim of the e-index is to differentiate between scientists with similar h-indices but different citation patterns. See Chun-Ting Zhang, The e-index, complementing the h-index for excess citations, PLoS ONE, Vol 5, Issue 5 (May 2009), e5429.