Having said that, I'm not aware of any banks who are selling properties directly to the public.
Most likely you will need to wait until the owner (the bank) lists it with a real estate company.
I recently saw a figure that there are an estimated 600,000 such properties out there currently, foreclosed but not yet marketed. However, I'm also finding that the foreclosing parties aren't always filing their sheriff's deeds promptly when they receive them, so the actual count is likely to be much higher.
These properties are typically winterized, boarded up, and may have lock boxes installed, but no sign in the yard.
There are a number of theories as to why the banks would do this, but one that makes a lot of sense is if they simply dumped 600,000 or more properties on the market, they wouldn't be able to get anything for them!
In all practicality, while you "could" make an offer, you'll probably have to wait till it's listed before they'll look at it.