If you want to pass a JavaScript object/hash (ie. an associative array in PHP) then you would do:
$.post('/url/to/page', {'key1': 'value', 'key2': 'value'});
If you wanna pass an actual array (ie. an indexed array in PHP) then you can do:
$.post('/url/to/page', {'someKeyName': ['value','value']});
If you want to pass a JavaScript array then you can do:
$.post('/url/to/page', {'someKeyName': variableName});