A lot of recipes tell you to salt sliced eggplant and let it sit for up to half an hour before cooking, to draw out bitterness. But Chowhounds think that, while large globe eggplants don't seem as bitter as they used to be, and smaller Italian and Asian eggplants rarely are anyway, there are other reasons to salt.
"Salting ... causes it to absorb much less oil" when cooked, bitchincook says. "The end product is also firmer to the bite." herby agrees: Salting "closes those pores that otherwise will suck as much oil as you give them!" gingershelley just likes the texture of eggplant that's salted before cooking.
Older globe eggplants can still taste bitter, however. The seeds are a pretty good indicator, hollyd says. "If the seeds are dark when I cut it, I salt ... if they're light, I skip it."
Photograph of CHOW's Eggplant Parmesan recipe by Chris Rochelle / CHOW.com