Try your web host first. Most of them offer their own version of a form to emil script.
Many people use the CGI form mail script from Matt's Script click here
It does a pretty good job and is relatively easy to configure.
There is a good PHP form handler called Jack's Script click here and if you want a PHP solution
Aside from that you could try any of the script sites for more alternatives than you can shake a stick at in any language you care to mention that a form to email script can be written in:
Hotscripts.com click here have form to email in Perl for CGI, PHP, ASP and one or two others.
If you know PHP you could write your own email script. It's not too difficult as long as you keep one or two security factors in mind.
First port of call should be your web host though, to see if they have their own form mail script. If you have CGI support you can use Matt's Script and if not you can try one of the PHP form handlers assuming you have PHP support. If your web host does not support CGI, PHP or ASP you're a bit stuck.