GNU nano is a console text editor, modelled after Pico. It is very newcomer-friendly due to on-screen menus with always visible keyboard shortcuts. Keybindings are configurable, and full undo and redo actions are supported. Nano even can be used as STDIN pager, and it provides fast syntax highlighting, even for regexps.
dte is a small and easy to use console text editor. Colors and bindings can be fully customized to your liking. It has some features useful to programmers, like ctags support and it can parse compiler errors, but it does not aim to become an IDE.
Tke is a full-featured and Tcl/Tk-based source code editor. It supports syntax highlighting and auto-indentation for multiple languages. There's support for a Vim mode, code snippet and clipboard management, bookmarks and multiple cursors. Tke provides a tabbed interface with a file system sidebar. It's also NFS and lock aware, extensible per plugins, allows regex searching/replacing, has configurable menus, and allows unlimited undo/redo levels.