I've made my own <span class="emoticon gasp">gasp</span>)
I just cut out some circles of scrap materials I had around home like bamboo, hemp and also flannelette. I backed them with PUL which waterproofs it and zig zagged around the outside. They are really slim, can't see them through my clothes, and surprisingly absorbant. And soooo much softer than the disposable ones! They seriously didn't cost me any money to make, as they were all made from scraps.
I've also bought some from here
But when I was using the disposable ones, I found rite-aid best value for money.
[Edited on 22/10/2009]