What, you may be asking, is a 'geoid'? A geoid is the shape a totally flooded planet would take if it were solely influenced by gravity, and not by tides or currents or other factors. In other words, it's the 'sea level' of the entire planet.
Thanks to the work of European Space Agency (ESA) and their Gravity field and steady-state Ocean Circulation Explorer (GOCE), we have a pretty good map of Earth's geoid, shown below. Regions of highest gravity are raised yellow lumps (more water piles up in those areas) and regions of lowest gravity are seen as dark blue depressions.
Further explanation: Bad Astronomy.
Update: Nathanial Burton-Bradford made a whole series of 3D images of our lumpy Earth. They're pretty cool even without 3D glasses, but dig out a pair if you can.