This took me a while to figure out, so I thought I'd document it here (quickly) to save others the hassle.

These are the steps to claim your bitcoin-cash safely.

Claim your Bitcoin Cash

1. Download and install Electroncash from here https://electroncash.org/#downld
   -- Do not download it elsewhere as there are poisoned binaries floating about.
2. Open your bitcoin-qt wallet
3. Generate a new address
4. Send all your bitcoin to this address.
5. Lookup the transaction on the blockchain explorer https://blockchain.info
6. Copy all of the outputs (the addresses on the left) into a text editor
7. Prefix each line with: dumpprivkey
8. Unlock your wallet if it's encrypted (it should be) walletpassphrase "passphrase" 900
9. In your bitcoin-qt app, go to Help -> Debug
10. For each of your dumpprivkey 1ofYourAddresses lines:
    a. Be extremely careful where you put these keys. Anybody can use these to spend your bitcoincash
    b. Copy and paste the line into your debug window of the bitcoin-qt wallet
    c. In your text editor, record the private key which gets returned.
11. Close bitcoin-qt now, you're finished with it for the rest of these instructions
12. Open electroncash and choose to create a 'standard wallet'
13. "Use public or private keys"
14. Paste all of the keys you recorded in step 9c, one per line.
15. Wait a minute and if everything worked out, you should now have your bitcoin cash (the same balance as your bitcoin was at the time of the fork)

Dump your bitcoin cash (optional, recommended)

Very few exchanges are working with deposits right now. I used viabit.

1. Sign up for https://www.viabtc.com/
2. Verify your email address and identity (via passport)
3. Deposit your bitcoin cash
4. Wait for 1 confirmation
5. Dump for BTC
6. Wait for 20/20 confirmations
7. Withdraw to your QT wallet.