转自：http://www.cnblogs.com/bird/archive/2007/03/13/673470.html
Inserting images into a RichTextBox control (the OLE way)
在RichText控件中插入OLE对象
A Windows Forms based text editor with HTML output
文本编辑器, 可以直接输出成html格式
A User-Searchable TextBox, RichTextBox, ListView, and TreeView in C#
在TextBox, RichTextBox, ListBox, TreeView中搜索文字
Insert Plain Text and Images into RichTextBox at Runtime
C# TextBox with Outlook 2007-style prompt
OutLook 2007风格的输入提示TextBox, 非常棒
Syntax highlighting textbox written in C#
高亮和自动补全textbox
Alpha Blended (Transparent Capable) TextBox and RichTextBox
PasswordBox: A Better Way to Enter Passwords
更安全的途径实现的密码输入框