Most Helpful Girl
Err well the usual ways is using mascara (that's the point of it - by making your eyelashes darker they will be more obvious) will make your eyelashes look longer. If you are still concerned you can buy fake eyelashes - you apply a bit of glue and then apply them to the top lid of your eye, just above your real eyelashes. As for any products? There are probably some but they're like anti wrinkle creams - unlikely to make any real difference.
There purpose are what others have said already :) Keep dust and crap outta your eyes.