If this isn't the wackiest piece of code I've ever written, then it is pretty close. There are three components to the page: a randomly generated grid, the changing letter sizes, and the "awesome song" in the background.

Random Grid

The toughest part was generating the random grid. The grid is made up of two types of components. The grid itself, and the blocks. Each the grids and blocks are have a visual and a data component. The visual components is handled by css,

Grid size

The first step is to determine the number of rows and columns that the grid will have. This is done by taking the ceiling of the quotient of the width or height of the container divided by the height or width of the cell. In this case the cells are 50x50 (40px with 10px of padding). I used the ceiling function rather than the floor because I wanted to fill the screen. Also the number of cells is recalculated on window resize.
$(window).resize(function(){
hcells = Math.ceil($grid.width()/50); //collumns
vcells = Math.ceil($grid.height()/50); //rows
}).resize();

Representing grid and shapes

Both the grid and the shapes are represented by 2-dimensional boolean matrices. The grid is initialized so that every cell contains a false value (meaning that grid position is not occupied).
for(i = 0; i < hcells; i++){
grid.push([]);
for(j = 0; j < vcells; j++){
grid[i].push(false);
}
}
Likewise, each of the block shapes has a shape array where the positions occupied by the shape are represented by a true value.
//default shape, single square block 
oneSquare = {
shape: [ [true] ],
className: "oneSquare"
};
//three wide by one tall
threeXOne = {
className: "threeXone",
shape: [ [true], [true], [true] ]
};

Placing Blocks

After the grid is initialized, each position is looped through and a block shape is chosen at random. Then the shape array of the block is compared the the grid starting at the current position. The block is placed into the grid if all the positions that will be take up by this shape are unoccupied.
function placeBlock(i, j, shape){              
//loop over space checking for occupation
for(x = 0; x < shape.length; x++){
for(y = 0; y < shape[x].length; y++){
if (grid[x + i][y + j] || x+i >= grid.length || y+j >= grid[x+i].length) {
return false;
}
}
}
//go back and mark spots as taken up
for (x = 0; x < shape.length; x++) {
for (y = 0; y < shape[x].length; y++) {
grid[x + i][y + j] = true;
}
}
return true;
}
If the function returns true then the block is placed absolutely in the grid using the cell size and i,j coordinates. The process of emptying the grid and filling it with random block is set to repeat 10 times a second. This makes the grid a pretty interesting browser benchmark.

Title

To spice up the title a little bit. I use the lettering.js a jQuery plugin to wrap each of the letters in there own div. Then on an interval the letters are looped through and a random size (within bounds) is chosen for each letter, and it is assigned one of 4 colors;
var colors = ["#0099FF", "#800080", "#0FF000", "#FF0000"];
function logoDance(){
$logo.children("span").each(function(){
randy = Math.random();
$(this).css({
fontSize: Math.round(randy*150)+75,
color: colors[Math.floor(4 * randy)]
});
});
}

Audio

The music is played through an HTML audio tag.To get the OGG version of the file I used Firefogg.

Summary

That pretty much covers it. Some arrays operations to create and fill the grid, lettering.js to jazz up the title page, and some quick html audio for the background music.