I some times think that I'm too obsessed with Ranma ½. When I think that I even if I am, there are other people who are or were as obsessed or even more obsessed with it than I am and there are worse things to obsess about. Sure there aren't that many websites devoted to Ranma as there were (were a lot thousands upon thousands) but that is because the Ranma fandom is aging and going on to new obsessions. I generally maintaining the things that I like forever.
Some fans have taken it upon themselves to translate the manga. That must have taken a long time. Multiple groups of fans have done it. There was the Ranmascan project (the most commonly found fan scans on the internet of the manga were done by the Ranmascan project), Studio Robb did several volumes (though those are no longer on that site), the defunct Wot-club (link goes to the internet archive of the site) had volumes 23-38 in text translation, and there was another text translation that I don't have a clue as to where it was or where it could be found now. Those are just the English language fan translations that I know about; it has been translated by fans in many languages. I have seen fan translations in Russian, German, Italian, Spanish, Chinese, and yet other English translations (then there are the official translations in more than 20 languages now).
Other fans have written fan fiction. A lot of fan fiction. At the time this was written (August 24, 2007) fanfiction.net had 8,629 fanfics. There were even more than that on it in the past. I know it had at least one crash that lost many of the fics and it had purged itself of many of the Ranma NC-17 fics and song fics as well. Not every writer of fan fiction had placed their fan fics on that website instead had personal websites or used a different fan fiction archive. The RAAC Archive had over 2,300 fanfics most of which are not on fanfiction.net. The Fanfiction Mailing List (link goes to a site where you can search its posts) was/is mostly about Ranma fanfiction.
Other fans spent countless hours just cataloging Ranma fanfiction. One such site was the Ranma 1/2 Super Highway, another one was The Penultimate Ranma Fanfic Index, and another one is Ranchan Totally Crossed Out! - this ones still active, another one is
I've gone on enough for now but I'll mention that others have spent countless hours drawing pictures, making crafts (saw some hand made P-chan pillows), making Doujinshi, translating the games, building and maintaining forums, creating websites, calculating Ranma's physical abilities (know of at least 4 different sites/people who did this), creating games, making music videos, shockwave games, translating some of the fan fiction into other languages, making audio books of some of the fan fiction, creating a webcomic based on it (for example Sailor Ranko), etc.