What's a good and reliable database on the pharmacodynamic and pharmacokinetic data of drugs both approved and unapproved?
For approved drugs, the Drugs @FDA database at CDER (Center for Drug Evaluation and Research) aggregates labeling information (which includes at least a cursory PD explanation and a listing of or reference to common PK data for the substance) for most modern drugs.

Unapproved drugs may be a bit trickier to find out about, but the FDA maintains a list of contract research organizations (CROs) who are running trials here, and the actual trials can be found on http://www.clinicaltrials.gov/, which will have citations for the papers that have been published.

Drugs in their earliest stages of development, i.e., internal to a pharma company, are likely to be kept pretty tightly under wraps.

I don't know enough about the governing bodies in other countries to know where any international data would be, but I assume you can find published papers for substances in those countries as well.