Very very basic ActionScript code to procedurally generate a Flixel level as an array of ones and zeroes. My first attempt at this sort of thing, turned out much better than expected.

FlixelProceduralLevelGenAttempt

var data:Array = new Array();

var xPosition:uint = 0;
var yPosition:uint = 0;

// Set x and y boundaries

var xHeight:uint = 40;
var yHeight:uint = 30;

// Higher number means more blank spaces

var whiteSpaceWeight:Number = 1.5;

// Iterate through vertical, horizontal spaces, assigning ones or zeroes to array

while( yPosition < yHeight) {
	while( xPosition < xHeight ) {
		
		// Creates solid blocks at top and bottom of space
		
		if ( yPosition == 0 || yPosition == 29 ) {
			data.push( 1 );
		} else {
			
			// Create solid blocks at left and right of space
			
			if ( xPosition == 0 || xPosition == 39 ) {
				data.push( 1 );
			
			// Makes every third line empty, creates empty horizontal space for player to move
			
			} else if ( yPosition % 3 == 0 ) {
				data.push( 0 );
			
			// Creates a slightly higher chance to create blocks next to other blocks horizontally
			
			} else if ( data[ data.length - 1 ] == 1 ) {
				data.push( Math.round( Math.random() ) );
			
			// Creates a slightly lower chance of creating a block not near other blocks
			
			} else {
				data.push( Math.round( Math.random() / whiteSpaceWeight ) );
			}
		}
		xPosition++;
	}
	xPosition = 0;
	yPosition++;
}

var i:uint = 0;

// Cycle through whole array and erase orphan blocks; emphasizes "platform" element

while ( i < data.length ) {
	if ( data[i] == 1 && data[i - 1] == 0 && data[i + 1] == 0 ){
		data[i] = 0;
	}
	i++;
}

// Generate and add the level using the created array

level = new FlxTilemap();
level.loadMap( FlxTilemap.arrayToCSV( data, 40 ), FlxTilemap.ImgAuto, 0, 0, FlxTilemap.AUTO );
add( level );