If you're talking about DIY breast forms...

You can also use pantyhose and rice... also lentils seeds, really any dry grains that won't fall through the weave of the fabric. One thing to keep in mind though, as the grain raises to body temperature, and as the form absorbs perspiration, the grain will start to smell more noticeably as the grain it is. So when choosing a filler, check the bulk section in your grocery store, and give it a good smell first to see how you feel about it.

Also large balloons filled with Sodium Polyacrylate gel. Finding the Sodium Polyacrylate is easy (try science education supply shops online, teachersource, for example).. the larger balloons can be a hassle to find in a good size. Standard balloons you buy in a toy or party supply shop will be way too small to bother with. The ones they use to put 'stuffed animals' inside of, tend to be better for this. Basically the balloon has to be vaguely breast-sized when completely deflated, because you won't be putting the gel in under pressure, and you wouldn't want it to 'pop' either... no one wants to find themselves with a bra full of body-temperature applesauce.

If you're willing to go all out for breast forms, some sellers on ebay sell some pretty hardcore breast forms made of silicone, going into sizes well beyond the useless "chicken cutlet' sizes. While making my one-last-ditch-effort to deal with my extended time off HRT, I purchased a pair. Based on my experience with breast forms in the past, I ordered a set 2-3 sizes larger than described (because I'm not a small girl).. but imagine my surprise when they arrived, and were actually way too big, and too heavy to be any use to me! So when it comes to sizing, be very careful, and always read the feedback comments.