Ask HN: How would you deal with DDoS?

In my recent memory - Posterous dealt with it once, the 4Chan and Tumblr fiasco and in the last few days, the Visa, MasterCard and PayPal mess.

What's a good way to deal with DDoS? Bonus points if you can elaborate more than "buy a stinkin' Cisco firewall"

EDIT: Do tell us your war stories as well.