You have a few options, all described here: Document and Deploy

To summarize:

- Through
**Mathematica Player** (which you
could see as another type of Flash
Player and is thus an executable
meant to view Mathematica
notebooks).
- Through a
**Language API** (which allows
you to embed Mathematica in your
language of choice, provided there's
an API for it. For instance, J/Link
or .Net/link for Java and C#
respectively. You can either use the programming language inside Mathematica, or create applications in the programming language that use Mathematica Kernel and objects.)
- Through
**webMathematica** (which allows
you to deploy to webservers and make
your work accessible through a
browser equipped with the necessary
plugin)

There's a couple more options. But these are the ones more approximate to your requirements.