Crushed coral is not a good idea, especially for some of the plants mentioned in this thread. It will raise the pH too high. Most of those plants prefer softer water with a sightly lower pH.
zpetrichko... I'm not sure if you commented with the intention of adding plants or if you were kidding. It's not a great idea to add any salt to planted tanks unless you are growing mangroves or other plants that have a root system that can "sieve" salt from water.
Crushed coral is dead coral, so... no, you don't need to add salt, but for living coral...most definitely you need salt, since it would require a saltwater tank!