Brabraland (funny name, I know) on eBay sells a wide variety of bras - Bali, Barely There, Bestform, Champion, Curvation, Danskin, Exquisite Form, Famous Maker, Frederick's, Gilligan & O'Malley, Goddess, Hanes, Just My Size, Lane Bryant, Lily of France, Lilyette, Maidenform, Olga, Oscar de la Renta, Playtex, Prospirit, Rene Rofe, Secret Treasures, Vanity Fair, Vassarette, Wacoal, Warner's and WonderBra. She also sells other undergarments - briefs, camisoles, lingerie and more.
Playtex bras, for example, start at $6.99 - that's the minimum you can bid. If you want to buy right away, you'll have to pay an additional $2. I waited it out and 'won' several at the starting price. Shipping for the first bra is $8. After that, it's a little under $4 each. The ones I got came with the original tags, including the price - $26(!) - the total I paid for 3 was $37, including shipping!
Other options are:
Natural figures offers low cost international shipping - 5.95GBP. Make sure to compare the prices - I found that their exchange rates weren't exactly the same as the bank (when I was checking, it was cheapest to pay in Pounds) - their prices start at $11 for a bra.
Bigger bras caters to women from size 32AA to 56K(!) Their shipping cost is $40 - pretty steep unless you need something pretty specific...
Freshpair that offers flat rate international shipping (to Israel, for example, it starts at $9.95) - look for it at the top of your screen when you load their page.