The Sea Level Rise Explorer is an interactive map that shows how high above sea level the coastal areas of the globe are. It's based on version 2 of NASA's Shuttle Radar Topography Mission, so it should be pretty accurate.
Above is Florida and part of the Gulf of Mexico seen from pretty high above. Since the map is based on Google Maps, it's easy to zoom in on very precise locations. Below are close ups of New Orleans, the Netherlands and Shanghai.
If you happen to live in an area that is barely above sea level, don't panic. A rise in the sea level won't happen overnight. There's still a lot of uncertainty in the scientific models, and the possible range of change is fairly big.
But the reason why this problem must be taken very seriously is the sheer magnitude of the potential impact. Hundreds of millions of people are located in these coastal areas, as well as important ecosystems. We can't afford to wait and see, because if we get to catastrophic runaway global warming, it'll be too late to change course.
See also: ::Flood Maps: View Sea Level Rise, ::Sea Level Rise this Century Higher than Previously Thought, ::The Intergovernmental Panel on Climate Change Report, ::The 4 Stages of Global Warming Denial