This library provides a general purpose reusable undo/redo system. Initial features include:

• Use either data,GUI or functional driven undo data suppliers (or all mixed together at the same time). Data driven undo data is supplied through interfaces and the event system. Attached properties are used to specify WPF undo data sources and you can easely declare custom Undo actions for functional undo data.
• optimized support for TextBoxes and RichTextBoxes.
• Supports data changes in streams. This technique allows for large data sets to be changed at once without overtaxing the system.

You can download the beta version from here.