GNU ed is an 8-bit clean implementation of the POSIX line-oriented text editor. Ed is the "standard" text editor in the sense that it is the original editor for Unix, and thus widely available. For most purposes, however, it is superseded by full-screen editors such as GNU Emacs or GNU Moe.
GNU Moe is a powerful, 8-bit clean console text editor for ISO-8859 and ASCII character encodings. It has a modeless, user-friendly interface, online help, multiple windows, unlimited undo/redo capability, unlimited line length, global search/replace (on all buffers at once), block operations, automatic indentation, word wrapping, filename completion, a directory browser, duplicate removal from prompt histories, and delimiter matching.
ted (Tiny EDitor) is a lightweight commandline text editor designed for scripting. It's intended to be an easier-to-use alternative to "ed". It is lightweight, scriptable, and easily harnessed by shell scripts, but doesn't suffer from the chronic user-unfriendliness that characterizes ed. It is also slightly more featureful than ed, and includes multiple editing buffers and built-in script handling.