Lifelike, interactive digital characters, serving as mentors and role-playing actors, have been shown to significantly improve learner motivation and retention. However, the cost of modeling such characters, authoring and editing their interactions, and delivering them over limited-bandwidth connections can be prohibitive. This paper describes a framework, authoring tools, and Web-based run-time environment that support the creation of training scenarios using digital virtual humans and other reusable 3D components. By conforming to the Humanoid Animation (H-Anim), Extensible 3D (X3D), and ADL Shareable Content Object Reference Model (SCORM) specifications, these 3D components are designed to promote reuse and interoperability at several levels. Recently, these software tools were used to develop prototype lessons in foreign language and cultural familiarization for use at the Defense Language Institute Foreign Language Center (DLI/FLC). These lessons include simulations in which the student, taking the role of a U.S. soldier, interacts with the local population of a foreign culture in authentic situations, using both English and the local dialect. Digital virtual humans are used to represent not only the soldier, and the roleplaying actors; but also a mentor who reviews language and cultural learning points, and provides remediation. Using these prototype lessons as examples, we review the potential advantages of the technology in other training applications.