While I can appreciate the desire to help organize, and to come up with creative solutions to a perceived problem, there are already forum tools at your disposal to tackle this issue, without creating more sub forums and more work.
You can search within any given forum, in addition to the overall forum search. If people simply get in the habit of including the state that the hang is going to take place in in the title of the thread, i.e. "New Jersey - Overnight hang this weekend", then all that is needed is to do a search withing the trip planning forum that already exists, enter "new jersey' as your search parameters, and you'll get all the info you need. Granted, the search engine will throw out the search term "new" because it's either too short of too common, but you'll still get all the hits because of "Jersey". The most recent will be the hangs coming up or just passed.
The only issue that will cause problems is if folks use state abbreviations. Then the search will automatically return a zero sum, due to the fact that it won't search for 2 character search parameters. So the only extra "work" required for anyone is to make sure they put "Massachusetts" instead of "MA" in their title, and so on. We simply have to take the extra second to type the full state name, and make sure it's spelled correctly.
Again, no need to reinvent the wheel here. Just applying a little bit of consistency in naming, and using the forum tools that already exist. While I applaud folks desire to come up with fun thread titles in order to try and catch peoples attention, perhaps in the trip planning sub-forum it would be better to simplify, and just keep it simple. Then again, as long as we start the thread title with the state name, it doesn't matter what the rest of the title says. So you can do "West Virginia - Walkin' in a winter wonderland hang, December 2012" as your title, and it will still come up for those searching for hangs in West Virginia.
Just a thought.