Have you been invited to a baby shower? Do you want to give the mother-to-be a creative and original gift that she'll actually end up using? If you don't want to spend 80 bucks on a commercial diaper cake, you can now make your own!

[edit] Steps

To form the top of the diaper cake, roll up a diaper, starting at the 'open' top end. Wrap a rubber band around the rolled diaper to stop it from unrolling.
Add 7 more diapers to the rubber band. For the middle layer, repeat step 1. Then add a new, bigger rubber band and add about 15 diapers. You can also secure them around a new 8oz baby bottle.
For the base, repeat step 2. Add a very big rubber band and add about 30 diapers.
Now that you know how big your cake will be, cut a circular base out of cardboard.
Place the largest layer of the cake on the cardboard base. Or, use a decorative plastic tray or even a pizza pan from the dollar store.
Remove one or two diapers and replace with a gift. Inside each layer, hide a surprise such as a coupon, a doll, some cream, or a piece of baby clothing. Use a bottle of baby lotion or shampoo in the center for stability.
Once you have the gifts inserted into each layer, assemble the remaining tiers of the cake.
Secure them together by carefully inserting 1 or 2 wooden dowels through the base layer and then carefully stacking the other two layers on top of it, being careful to get the dowels between the diapers and not through any of the diapers.
Add a ribbon around each layer to cover the rubber bands.
To finish off (and help transport) you can wrap the "nappy cake" in cellophane or netting. Tie at the top with a bow, or add a stuffed animal to the tie for a "topper" to the cake.
An alternative to rolling up each diaper is to use the diapers as they come, placing them side by side and forming a rolling circle, place a large rubber band or ribbon or both around each "tier".

[edit] Tips

One of the things that is very helpful is seeing the expected result before setting to work. Flickr.com is a great place to search for images of diaper cakes, and then it’s much easier, both in the building process, but more important, in decorating.
Find a good video tutorial that takes you through all steps, from design to decoration.
Most packages have a see through side panel or a picture of the diaper on which you can see the design on the diapers. If the design colors are really busy it might detract from the overall look.
Use size 2 diapers or larger. That allows the mom to enjoy the diaper cake longer before needing to take it apart. Be sure to let them know if any of the gifts are perishable.
On the other hand, using size 1 diapers will allow the mom to have some on hand to use right away. You could also make the top 2 layers out of one size and the bottom layer out of a larger size, depending on the number of diapers in the bag you buy.
The number of diapers in each layer are just an indication and will change depending on the brand of diaper and how tight you wrap them.
For a fatter cake, add a ring of diapers to each tier.
You can buy commercial diaper cakes, but people will love the fact that you've put effort into the project.
You could do this project with cloth diapers if the parents are environmentally conscious. The cake would be smaller because you don't need as many diapers and they're more expensive.
You can use the same directions, but instead of using diapers, use hand towels, decorate with small flowers and add a few small kitchen utensils, and use it as a Wedding Shower gift to the bride to be.

[edit] Things You'll Need

At least two packs of diapers
Gifts to hide (i.e.: pacifiers, washcloths, onesies, mittens, socks and baby supplies like lotions, rash cream and baby wash)
Rubber bands (various size ; you can find a variety pack for less than a dollar at Target)
Wooden dowels
Cardboard large enough for the base
Colorful ribbons and bows
Netting or cellophane