I started with a plastic shoe box, which I thought could be used to store the accessories and possibly as the "bath tub." I added a $1 wash cloth, a $1 hand towel, and a $1 bottle of baby soap (which I watered down quite a bit). For clothing, I bought a $2 newborn size onesie and made some cute felt diapers following Jessica's idea (here). Then, I added a tiny rubber duck that I already had in the house and a small cup (lid) for pouring. Done and done for less than $10 and a bit of work (and really, it could have been done cheaper).
I forgot to get a pictures. Lame, I know. Here's a picture from the original diaper post: