MarkdownPlugin is a plugin for jEdit that can render Markdown text from the current buffer or from selected text. The resulting HTML is written to a new buffer or copied to the clipboard. The plugin can also show a preview in a Web browser (using the Info Viewer plugin).
Markdown is an easy-to-read, easy-to-write plain text format. Using this plugin you can convert it to structurally valid XHTML (or HTML).
Download MarkdownPlugin.tar.bz2 then unpack it to YOUR HOME DIRECTORY/.jedit/jars. It's all.
Run jEdit and find Markdown submenu in plugins' menu.