Very accurate sundials with easy adjustments for longitude and latitude. These are much prettier than the "World's Most Accurate" sundials, and much cheaper than the "Precision Sundials".
dead link: http://atensundials.com/
This sundial uses specially cut masks to make shadows in the form of a digital readout. It doesn't try to show time intervals of less than ten minutes, so it isn't very accurate, but it sure is nifty.
This site offers double sundials, to tell both solar and time zone time, and a helical sundial which uses special lenses to focus a line of light, instead of a shadow, on the current time. The second is adjustable in two ways, the angle can be set for your lattitude (no need to to custom build to location) and the time markings are on a slider to adjust for daylight savings time and the equation of time.
Sundials and plans for sundials calibrated for the specific mounting location. This calibration is necessary to adjust the shadows for the height of the sun (lattitude adjustment), these clocks go further and adjusts for longitude so the clocks will display time-zone time instead of solar time. Standard time or daylight time zone calibration is an option. Even still the sundials will vary because of the "equation of time" due to differences in the speed of the Earth at different places along its orbit of the sun. So these come with a reference table for the adjustments needed, which you have to do after reading the sundial.
qz thoughts