Probably the easiest software is the free wordpress for blogging (http://wordpress.org/ ) which you can install on your server. There is a large extension base so you should be able to find whatever you need.

try looking into a php script that forwards the content of a text box to a provided email address (yours), and sends a confirmation mail to them (if wanted). If you want to set something like a forum up, it could get a bit complicated, but php does that too.

Well, if you are looking for an easy way to build, then you should check the page builder options offered by your hosting company as they will usually contain many differente template to get you started. You might want to find one that is geared more to blogging, and then you can actually just copy/paste and insert flash and html modules with information that you want added. For the buisness to add and manage information this is refered to as subscription based servies, and requires a higher bandwidth than normal.

To design an interactive website, you need:
HTML, Javascript, a server side language, a database, AJAX and very SERIOUS programming knowledge and experience.
Failing that, you can try to download a thousand “free scripts” and/or CMS, and try to adapt them to your needs. This will take you longer than learning to program in all existing languages (without talking of the frustrations and irritations you WILL suffer by not understanding the “WHY” that script does not work…
Failing that, get a freelancer to work for you, but BE PREPARED to pay the price! An interactive website like the one you propose will take some serious programming to do, and experts are not cheap.
You will, surely, get a hundred amateurs to quote you a few hundred dollars, but NONE will supply the goods. Be prepared for several 1000′s!