Organize, manage, and analyze your sales data using Excel.
BSEditor: Lokad Sales Forecasting for Microsoft Excel is an open source add-in that provides sales reporting and sales forecasting.

This software requires a subscription plan to be fully functional (starting at 0 USD / month with the Partner plan).
Features
Native integration into Microsoft Excel 2000 or higher.
Import sales data from 20+ business applications into Excel.
Explore, visualize and organize your sales data through Excel.
Upload your sales data to Lokad in One Click.
Define customizable forecasting tasks (per day, week, month).
Download your sales forecasts through our forecasting technology.
Windows Installer provided (uninstall is supported).

Not having Microsoft Excel? Then, try Lokad Desktop Sales Forecasting, its a stand-alone windows application.

Resources
Getting started: get your sales Forecast report in Microsoft Excel.
Importing data: 20+ applications supported, connection String syntax.
Calculate safety stocks with sales forecasting (guide).
Developer guide: customize or extend the application. you can free download Lokad Excel Sales Forecasting 1.3.0 now.