This weekend, I had the opportunity to learn what to do when one's wallet is stolen. I would have preferred read about it instead of learning through personal experience, but now I can pass the information on to you so that you can learn by reading.
1. Lower the limits for how much can be charged to your credit cards or withdrawn from your bank account on any given day. That way, when anyone (including you) tries to charge or withdraw more than the limit, you will be called to confirm the purchase or withdrawal. Yeah, it's a pain if you're trying to buy something or are going on a trip and need a bunch of cash, but it prevents other people from running up thousands of dollars on your credit card.
2. Don't keep lots of money in your checking account, so any huge charges on your debit card will be declined due to insufficient funds (sometimes it really pays to be broke). Also, don't keep more than one or two credit cards, and be sure to close all accounts that you don't use anymore.
3. Don't keep your Social Security number in your wallet or purse (thankfully I didn't either).
4. Keep the account service phone numbers for all credit and debit cards in a safe place at home. Thankfully, my credit card company contacted me as soon as someone attempted to charge a large amount to my card, and they were able to give me the numbers for my other credit card and my bank. Thank you MBNA for saving me some time and grief.
5. File a police report immediately (duh). Many places require a police report number to verify that it was theft and not just you being a dumbass.
6. Even if your SS card wasn't in your wallet, you could be vulnerable to credit fraud. Call any one of the three credit bureaus (Experian, TransUnion, or Equifax) to put a fraud alert on your credit report. No need to call all three--when you place a report with one agency, they will automatically share the information with the other agencies. This will require any credit company to contact you directly to authorize new credit applications so that no one can open new credit under your identity.
7. Create only good Karma so that it doesn't come back to bite you in the ass later on. Even if you don't believe in Karma, avoiding gossip and keeping a positive attitude never hurt anyone.
I got lucky: I only had about $10 in cash, my credit card companies followed up right away so that no one was able to charge to my cards or gain access to my bank account, and there wasn't enough personal information in my wallet for anyone to do anything (I hope!). Be careful and protect yourself so that if God-forbid anything like this happens to you, the damages will be minimal and you'll be prepared to take care of it quickly.