I normally don't carry more than $100 cash, but one day I managed to get my hands on about $2000 (can't remember why), and I was riding home on the metro. Late at night. Halfway home I realized that I'd be walking across a large parking lot late at night in a dodgy area, and even with plenty of lighting, my purse might be in danger. So I started stuffing money in my bra. Not on top where it could be easily seen, but underneath. I had all of that cash, in $20 bills, along with my driver's license and debit card, stuffed in there!
I have never been so happy to be well-endowed in my life. For what it's worth, I didn't have a problem in the parking lot. There were lots of people around, even at 10:30pm.