From http://www.jas.com/jasbits/

Idaho Computing has taken multimedia one sense further, by developing a PC
add-in board that uses chemicals to generate scents on your computer.

The $199 ScentMaster can produce 36 distinctive smells, such as "roses," "new car,"
"roasted coffee," and "dead animal in wall."  The scent board functions in much
the same way a sound card does, except instead of playing sounds, ScentMaster
mixes three chemicals (primary scents) to produce the various aromas which are
wafted into the atmosphere via a small spray-emitter module.

Available for a Mac soon, too.

(Internet World, April '95 p.16)

[BTW: actually a gag that fooled many]