We have just released a beta version of an automated financial planning tool: http://www.fiveminuteretirementplan.com/
This tool dynamically creates ETF portfolios based on an investor’s risk tolerance and time frame.
The site includes a detailed description of the methodology used to create the financial plans along with links to a spreadsheet with the exact calculations. You can see the methodology and download the spreadsheet here: http://www.fiveminuteretirementplan.com/Home/Methodology
Our goal is to create a simple tool that allows a user to explore various "what if" scenarios to see how changing contributions, retirement date, etc. will affect their retirement plan.
Please reply with any improvements you think could be made to the site or methodology.