What do you want to know about 'em? They're anything with a salt content above freshwater but below seawater (Water density: 1.005-1.020?) Somethin' like that. Fish for brackish water would be archerfish, scats, monos, green spotted puffers, Figure-8 puffers, bumblebee gobies, mollies... A lot of brackish fish get very large from what I've read. Plants that work in brackish seem pretty limited, but java fern and java moss are supposed to work if acclimated to the salt content slowly. I'm planning to start up a brackish tank sometime.
5gal: 2 Black Mystery Snails
10gal: 2 Mickey Mouse Platys (1M1F), 1 African Butterfly Fish, 3 Khuli Loaches
29gal: 1 Green Severum, 1 Convict, 3 Bronze Cories
55gal: 5 Bloodfin Tetras, 6 Black Skirt Tetras, 1 Blood Parrot, 1 African Brown Knife, 1 Striped Raphael, 1 Ropefish, 2 Clown Loaches, 1 Yoyo Loach, 1 Angelfish