There are many online resources for free CGI scripts. Go to the Finding CGI Scripts section of this document for a list of some. The Gazette reviews interactive tools in almost every issue. A site is generally made interactive using a programming language .
Programming is much more involved than HTML and requires much more training.
There are five general approaches you can use for adding interactivity. The hardest is also the cheapest, and vice versa. Prices can range dramatically depending on the scale and complexity of the desired project. This can take many, many hours, and can be extremely tedious. Furthermore, if you do not already know how to program, you will have to learn.