Touch Design Lite is a free version of the Touch Design application. Developed for iPad this tool provides a rich feature set including diagrams organized into model projects, context sensitive link creation capabilities, element resizing, drag and drop over elements (e.g. nesting packages), detailed element editors where applicable and in-place editing for others.
Current supported diagram types within the suite are
Use Case Diagrams
For a full overview of supported features for each diagram type, including detailed screenshots and help content see http://www.plumhead-software.com/touchDesign/features
Coming in future releases support will be provided for other UML diagram types. For details on this and a full product roadmap see http://www.plumhead-software.com/touchDesign/roadmap