The following popular investing tools have been developed by members of the Bogleheads forum.
The backtesting tool is a spreadsheet to backtest portfolio returns from 1972 to present [1985 to present if you want to include certain Sector/Tax-Exempt funds that started after 1985] of various Vanguard Mutual Funds. This tool is customizable and you can add the returns for any mutual fund.
Many creative investors break the mold and build their own portfolios. These spreadsheets are designed for quick experimentation and can all be modified to study any asset allocation you wish.
Portfolio Visualizer provides online portfolio analysis tools for backtesting, Monte Carlo simulation, tactical asset allocation and optimization, and investment analysis tools for exploring factor regressions, correlations and efficient frontiers.
An Excel spreadsheet that uses a macro to compute the values of each I Bond in a portfolio. It differs from the Savings Bond Calculator and Savings Bond Wizard in a couple of ways:
Computes the values for twelve months at a time instead of only one.
Works with any denomination; not just the ones that paper bonds were issued in.