I've administered a few bulletin boards for gaming sites, and it can be a lot of work - you need to have a clear idea of what you want the site/board to accomplish, and communicate that clearly to your audience (potential forum members!) - including being specific regarding what kind of content is/isn't appropriate. Hosting a forum/website for a topic that you are passionate about can also be a lot of fun, as well as a huge learning experience.
That being said, I offer my help in any way you may need it - being the huge sci-fi fan that I am!
Allsortshop's questions are an excellent place to start - as you think about your answers, consider that most "free" web hosters are not likely to give you the kind of space and/or features that you need to run a bulletin board - you may need to do some searching if this is the route that you want to go. If you decide to pay for hosting, note that it is customary and entirely legitimate to solicit (not necessarily demand!) a small donation from members to cover your costs - prospective members should have the option to decline.
As Allsortshop has indicated, phpBB is a totally free, open source bulletin board that comes with a TON of features - check them out
here. Your host needs to give you php and MySQL as part of your hosting package.
And now, a question of my own!
What aspects of science fiction do you intend to deal with? Are we talking movies, television shows, fiction, comics - any or all??? As you are no doubt aware, "sci-fi" is an incredibly huge topic, and each "sub-genre" can have (and has had!) entire web sites devoted to just that one small piece of the pie. Nailing down where you want to start will give those of us that indicate a desire to help an idea of where to go from here. (I don't mean for my question to start a discussion that gets us in danger of getting off topic in this forum. Should this become the case, those interested can rely on e-mail or private messaging to continue. At this point, I simply want to get you thinking about the direction you want to go in!! - no doubt you've done a lot of thinking already -

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Edited by The Architect, 17 April 2006 - 08:23 AM.