It depends. Before my parents died, they made my sister and me co-owners of their checking and saving accounts, so we simply closed the accounts by writing a check.
Their insurance policies were paid off by check in a few weeks. We were also named beneficiaries of their CD's, so we cashed them in immediately. The house was put up for sale, and sold a few months later.
They had no investments, but the executor will usually cash them out, and the investment firm will write checks to the heirs after proof of ownership is presented to them.
If a will has been written, things progress faster than if the estate must go through probate. Here in Texas, probate is fairly simple, but in some states, it's a long, expensive process.