Bendon is offering 50% off all bras until Sunday, the 22nd of May. Although the code works on sale items as well, the discount will apply to their original pre-sale prices (or RRP).
I have price compared some bras on sale, expensive luxury ones and new season styles and found that you'll only get a good deal on the new season styles which sell for their original prices across all other stores.
* Heidi Klum Liberty Shine contour bra for $34.98 vs. $69.95 at DJs and Capri
* Pleasure State - Vip Lorna Elise Contour Balconnet Bra for $49.98 vs. $99.95
Sale items are on sale other places as well, for example Myer seems to be very competitive at the moment on bras so I found it hard to get a good deal on those. Some of the most expensive full priced bras I've found on sale elsewhere as well, so I would recommend sticking with new season styles.
FYI - the code does not apply to Stella McCartney Lingerie.