Sybil's Secret Service would be happy to have you.
Our site: http://sss.darkjedi.org
We were founded quite a few years ago: played through FFXI for years and tormented ourselves with FFXIV 1.0 for a while. We're floating around the 60 member mark, many FF veterans, and quite a few MMO players who are new to the franchise, too. There are a few members that are a little bit younger (mid teens), but many of us are well into adulthood (many of us joined when we were in our teens.. I'll be hitting the 30-year mark myself this year).
As far as our "style", we're officially very casual, but we've got a solid population looking forward to running lots of end-game. In terms of organization, we employ a military-style chain of command at the site to make administration easier, but we don't expect you to give up on life to come out and play on a regular basis. We'll be establishing some "official" times to get together for runs, but we wouldn't dream of having penalties for not showing up. The end result is a very well-organized guild, great communication, plenty of opportunities to run content, and good times all around.
Feel free to visit us any time, and if you have questions, feel free to PM me. :) Edited, Aug 21st 2013 10:00pm by IronLight