TOPEX Sea Surface Height
Sea surface height is measured from altimetry by the Topex/Poseidon satellite. Every 10 days the complete earth is scanned by radar-like sensors on the satellite. Below is a map of the Hawaiian archipelago region. The colorshading and contour lines show all the hills and valleys on the sea surface, and these topographic features can be used to estimate the direction and strength of the geostrophic component of ocean currents, the strongest of which are shown on this map. This particular release of the data is a near-real-time product from the NOAA Laboratory for Satellite Altimetry. Click on the image to see it in full size.
SeaWiFS Ocean Color Data
Here's something from a different satellite, a new one called SeaWiFS. This one is more like a camera and sends back images of ocean color, which can be used to estimate ocean productivity. This is useful to know since productive areas may be good places to fish. Click on the image to see it in full size.
AVHRR Sea Surface Temperature
The next two images are borrowed from the NOAA/NESDIS group working on satellite-derived SST. For similar images see their homepage. Click on the images to see them in full size.