The placenta helps a TON with the hormone crash! I have never used it dried but I had it raw/frozen and it made a huge difference.
Other than that make sure you are on a good VitD3 (oil based, from cholecalciferol), a good b-complex, magnesium citrate, and you get plenty of good fats (like coconut oil). And don't overlook the power of sunshine and fresh air to lift your mood.
Lemon balm can help with depression but it can also reduce milk supply so I would use that carefully. Blessed thistle can help with depression as well and motherwort is awesome for anxiety. There are different beliefs about the safety of these herbs while nursing so research it on your own and make the choice. I have used motherwort and blessed thistle with an older nursling but not a newborn; I would do it if I was experiencing symptoms though.
Melatonin is great for getting to sleep, which can be difficult with depression and anxiety, and I have taken that while nursing.
I would also do some Emotional Freedom Technique work on the experience with PPD last time so that I could go into this pregnancy with a fresh start and not bring in the expectation of a repeat experience. : http://eft.mercola.com/