The FDA has published its yearly list of new, withdrawn and revised CDER guidances. This list provides a very good overview about the agency's activities regarding these documents. Guidance documents represent the Agency's current thinking on a particular subject and are an important part to define cGMP. Nevertheless, an alternative approach may be used if such approach satisfies the requirements of the applicable statute, regulations, or both.

You can find the list here:
http://www.fda.gov/cder/guidance/new_revised_withdrawn_2007.pdf
An overview of all published documents can be found here:
http://www.fda.gov/cder/guidance/comprehensive_list.pdf