There is no shortage of such services; but they all cleverly include a banner ad as part of form built for you. Having seen many such services, I have made one which DOES NOT force you to put an unwanted ad on your page!

Enter TechnoSoft21 ViralTraffic, all-new free service which provides a form-builder and a form processing script to anyone who needs it. All you need to do is head to site, fill out a form which generates code for you, then copy and paste code into your own website. When you view your site, you will see that it DOES NOT have a banner ad or any other ad on it! You will be ready to get tidal wave of traffic to your site! To get started, just go to http://www.technosoft21.com/viraltraffic/

P.S. If for some reason or another you don't want to use TechnoSoft21 ViralTraffic, you will probably have to construct your own form processing script in FrontPage WebBots, PHP, CGI, Perl, C, AppleScript, Python or another language. It's tough work, but it's fun. If you're game enough... go for it!