HotScheme
A Scheme interpreter applet, with source code and documentation.
Jscheme
An (almost complete) R4RS implementation of Scheme in Java with a seamless and easy to use integration with Java through the Javadot notation. [Open Source]
Kawa Java-based Scheme System
Scheme environment, written in Java, compiles Scheme code to Java bytecode. [Open Source, modified GPL]
PS3I, The Persistent Server-Side Scheme Interprete
A nearly R4RS-compliant Scheme implementation written in Java and Scheme, which is multi-user, multi-threaded, and aimed to run on webservers (as servlets). Based on a previous Scheme-in-Java implementation, Jaja, by the same author.
SISC: Second Interpreter of Scheme Code
Extensible Java-based interpreter for Scheme. The entire R5RS Scheme standard is supported, including a full numeric tower as well as full support for first-class continuations. [Open Source, GPL]
Skij
Scheme interpreter designed to provide smooth, interactive access to all facilities of the Java environment for rapid prototyping. [Freeware]
The Scheme Package
Java library implementation of Scheme language. Goal: easy use in Java applications or applets to make them extensible.