Toba - Java-to-C Translator: translates Java class files into C source code to allow making directly executable programs. For stand-alone applications, not applets. [Freeware] - http://www.cs.arizona.edu/projects/sumatra/toba/
Webcream - Claims to convert Java GUI client-side applications to HTML/JavaScript-based front end with no recoding. [Commercial] - http://www.creamtec.com/webcream/index.html
Excelsior JET - Converts Java applications to optimized conventional Windows EXE and DLL files. [Commercial] - http://www.excelsior-usa.com/jet.html
GCJ - The GNU Compiler for Java - compiles Java source or bytecode to native machine code. Most APIs are supported, except the AWT and Swing. [Open Source, GPL] - http://gcc.gnu.org/java/