Opening a bank account without using your SSN.
There are millions of illegal aliens living in the US. They have no legal US documents, no SS numbers, yet almost all of them have US bank accounts.
Bank account that does not have your name, SSN, and address will be virtually untraceable by your wife.
I have no idea how illegal immigrants open bank accounts without real documents, but millions of them do it; so whatever they are doing must be working.
Opening a bank account like that may have perfectly legitimate and ethical reasons. Identity theft is a growing problem affecting millions of Americans a year. Opening a bank account that is not linked to your name/SSN/address is a good way to avoid having your money stolen by identity thieves.
Buy collectibles your wife does not know about.
Many small things sell for thousands of dollars on Ebay and seem to be appreciating in value over time. Only do it if you understand the particular collectibles market. Avoid paying by check/wire
transfer/credit card from the account your wife has access to as much as possible.
Transferring money into foreign and/or offshore bank account.
Transferring money into foreign bank accounts is probably not worth it unless you have $100,000 or more to transfer. For smaller amounts it seems easier and safer to just withdraw and keep money in the US. I would also highly recommend getting financial advice from an expert in transferring money to foreign account before doing that.
There can be no records of money transfers or written checks between your US account(s)and your foreign account(s).
You can take up to $10,000 out of the US every time you travel abroad, plus you can withdraw $400 or so per day from each one of your US bank accounts from ATMs while you are abroad.
You will need to report the interest you earn on your foreign account(s) to the IRS, but you do not need to mention the account existence to anyone. Your bank statements can not be sent to your home address (or any address your wife has access to). Foreign accounts are not likely to be found during divorce unless your wife (and her divorce attorney) already knows where you have them.
Buying property abroad.
Foreign property ownership might be even harder to trace than foreign bank accounts. Your wife obviously can not know about your foreign property. You probably ought to keep it largely a secret from anyone. You also can not pay for it directly from your US bank account.
Buying property abroad is a complicated subject. You need to know the real estate law in the country you will be buying property at. Like offshore bank account, it's probably not something you'll be doing if you have less than $100,000 USD to work with. You should definitely hire an expert in this subject if