Estate planning is one of those topics that most people avoid dealing with until they're forced to. Because of this, many people find themselves in a bind when a loved one passes away. By having an up-to-date estate plan, as well as keeping your key documents well-organized, you can ensure your partner or heirs are not over-burdened in a time of loss.
It'd be wise to have an "estate-planning folder" tucked away somewhere safe, with updated copies of all your pertinent documents. This naturally would include a will, and for most investors, a living trust. It should also include up-to-date copies of all your beneficiary designations (who gets the money if you die) for your retirement plans and life insurance. Lastly, it should include a list of all of your assets held by other parties such as bank and brokerage accounts.
It'd also be wise to include in this folder, copies of any medical directives, durable powers of attorney and living wills you may have. These documents give specific instructions and delegate specific decision-making ability in the event that you become incapacitated. Likewise, you should include a list of any last wishes you might have regarding your burial and memorial service.