Datasets by Category

Ocean

Levitus Climatologies a series of uniformly gridded three-dimensional oceanic datasets.

Air/Sea Interface

These include both atmospheric and oceanic data.

Surface Climatologies values for a "normal" or average year.
Surface Data data at the air-sea interface.

Atmosphere

Oort (1983) gives global atmospheric circulation statistics. This includes an atmospheric surface climatology.
NCEP-NCAR Reanalysis Project, global gridded analyses.
ECMWF gridded global analyses
NOAA summaries of station-based data are available monthly gridded, monthly by station, and daily by station.

Topography

Global U.S. Navy bathymetry plus land heights at 5' by 5' resolution (i.e. 1/12 degree by 1/12 degree). Also available at 1 degree by 1 degree.
NOAA United States topography with 1/120 degree (1/2 minute) resolution (i.e. just under a square km).
Peltier's Ice Age Paleotopography is also available.

Globally, higher resolution data is available from NOAA GCDC on CD-ROM: it is called the Global Land One-Kilometer Base Elevation (GLOBE), currently (Apr 1996) version 0.1.

Forecasts

Tropical Pacific SSTA forecasts are here.