A critique and list of problems with string theory as a theory of quantum gravity, from Warren Siegel's website. There you can also get his book on string field theory and other important publications.
Work by Daniel Friedan on a different sort of theory. The introduction has extensive comments on the present situation of string theory.
A dialog written by Carlo Rovelli presenting an impartial version of the lively debate between string theory and loop quantum gravity.
An assessment by Lee Smolin of the state of research in quantum gravity, including a careful consideration of the state of string theory as a quantum gravitational theory.