The Three-Fund Portfolio is an investing staple on the fantastic forums at Bogleheads.org.  While the allocation percentages are not static and may vary by individual investor, the one represented here is perhaps the most popular starting point.

Asset Allocation

• 40% Total Stock Market
• 20% International Stocks
• 40% Intermediate Bonds

Performance

Change the home country to translate the portfolio to local assets, currency, and inflation