DNN's architecture is built around a form.... which means you can't embed further form tags into it.
You can either;
                          Build an asp.net User control and add that control as a module (this is quite simple).
                   or  use IFRAME to put a 'window' in your page to a standard page outside the hosting website. This works just fine but has certain limitations ... its a quick fix.

Hey Komrad,

I don't know of a module that does what you're wanting to do specifically, however, you may want to take a look at this KB article and see if you can adapt it for your script:

http://support.powerdnn.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=77

If you can post your form here, I'll see if I can write a generic KB article about how to use form tags in DotNetNuke.