I made a diaper cake for my sister's baby shower last month and it was a total hit.  Here is the picture:
I've also made one for a baby boy:
I use huggies size 1 diapers and don't use glue or anything to to keep them together.  I just sort of roll up and hold together as many as I can then tie a string around them to hold them together.  I just keep adding the groups together and holding them together with more string.  When it gets big enough, I use baking dishes for molds for each tier.  I eventually cut out any extra string except for the very outside of the layer, and that is hidden beneath the ribbon.  Then I just tuck in lots of goodies like Boudreaux's, J&J baby wash, some pacifiers, and I top is with a soft plush rattle.

I must've been on the same wavelength as evryone else when I started this.  I started working on in way back in February but I got bored and put it down so many times that I didn't finish it until about a month ago.  I used a Bernat baby cotton in a bright lime green with a purple border.  I used a single strand and stupidly didn't change the needles so it ended up a lot bigger than I was expecting.  I do kind of like that the gauge is more loose though, because it feels lighter (more like a summer blanket).  Oh well, this was definately a live and learn project for me.  It was the first time I've done something needing more than one skein so I made the fatal mistake of not checking dye lot.  Oops!  It looked fine when I was working on it, but when I finished I wanted to make sure it wouldn't just unravel in the wash.  This was my first go at intarsia (sort of intarsia with the border). Well, the purples match up fine, but after washing there was a decided line through the bottom half where the greens change a slight shade.  Oh well, here goes: