List of Free code Captcha
A C# port of Jeff Atwood's ASP.NET Captcha Control.
Captcha Control (C#) allows users to add a captcha to an asp.net page. The control supports declarative settings of fontsize, font family, color, captcha length, background image, character set, success, error and buttons' text. Supports audio - reading out the captcha text.
Capthca in Sharepoint 2010
Modified the Captcha control of asp.net so that it can work with Sharepoint 2010.
Distinct CAPTCHA Web Service
Distinct CAPTCHA used to add CAPTCHA to asp.net, InfoPath and SharePoint. The web service supports two methods one for generate and one to validate
Improved CAPTCHA Control ASP.NET 2.0 C#
Improved C# port of Jeff Atwood's custom CAPTCHA control (image verification against robots).
ASP.NET MVC compliant captcha generation library.
MyCaptcha! free Asp.net Captcha control
MyCaptcha is a free opensoruce ASP.NET Captcha control written in C# 3.0.
SolidQ Captcha Asp Net and SharePoint Control
SolidQ Captcha Asp Net and SharePoint Control is a new way to validate forms. Is based on human perception to distinguish colors. The user select the correct color and drag and drop it to the validation area. It's developed in asp.net, vb.net, jQuery and Ajax.
XCaptcha - CAPTCHA Images for ASP.NET MVC
An extendable and simple to use framework for creating CAPTCHA images.