SynEdit is an advanced multi-line edit control, for Borland Delphi and Kylix (C++Builder mostly works, but is unsupported). It supports syntax highlighting and word-wrap, and it includes code completion and templates components, and exporters for html, tex and rtf.
It is a pure-VCL/CLX control, meaning it is not a wrapper for Microsoft Windows controls and so no run-time library is required.