Almost any web design software will work... but the good news is that you can get the best there is for relatively cheap. Dreamweaver. If you are a student (or you have a student in the household) you can get the Academic version for about $180. Or an older version (like DreamweaverMX) for even cheaper.
From there all you need is a domain name (a dot com, dot org etc) which will run you about $8 a year, and hosting, which will run $60-$100 a year depending on who you choose.
(There are scads of
free web space sites out there, but for something as potentiall big and feature full as you describe, they'll probably not work for you.)
Just my opinion: You can find web design software as cheap as $50 on the shelf of your local software store, but within a few months, you'd find yourself wishing you'd spent the $180 for the software that will do everything you want.
... and as for a forum, one of the best ones out there is free:
http://www.simplemachines.org/ You'd use it in conjunction with your site.
Hope that helps with the basics.