Warren Buffett recommends investing into S&P 500 (instead of any managed fund), but aside of that his recommendation is pretty much identical: forget about it and focus on your primary job/business.
Funds suggested by patio11 are very popular index funds. They're broader than S&P 500 but it's the same principle.
Warren Buffet's advise is great but I have never understood why he picks S&P 500 vs the Nasdaq? If you look at almost any time period the Nasdaq has outperformed the S&P by at least 1% (Annualized Growth Rate) which compounded year after year is a significant difference over your working lifetime (~%50 greater return after 40 years)! This is what I have been doing for the past 10 years and I am >2% (AGR) over the S&P.
Warren Buffet likes companies with strong revenues and profits, and importantly, companies that pay shareholders/owners. Nasdaq Composite is largely tech companies whose main value is growth potential and most of their profits get reinvested in the business.