I don’t disagree completely with peterb either. If one has been out of the market I think this is a great time to start dollar-cost-averaging back in over the next 1-2 years to get back to whatever portion of your retirement (long-term money) portfolio you plan to have in stocks for the next 10-20 years.

Still, a hefty cash allocation (for me it’s 40%) is important for stability and to play a little defense.
Also, if you want to use the money within the next 5 years or less (e.g. to buy a home, start a business, etc) I would not put it in stocks.