Sidebaring the trello is an excellent idea; I'll poke our mods about that. In the meantime, here's our development timeline for anyone else who is interested: https://trello.com/b/ICAylAE8/eve-missions-0-x-development
The site isn't really in a release candidate state yet. The skeleton is there: we have the database, CMS (cloudflare and our own server!), auth system, and mission entry. We're having troubles getting the "Runners" section off the ground, though. Accepting and completing missions is next on the list of things that need to get done.
From what I've seen, the greatest challenge is keeping interest going. We have a small core of very dedicated coders, but they can only give so much time to the project. Our IRC is the heart and soul of the team. You can tell what's going on (or what isn't going on) based on what is (or isn't) being said there. For a few weeks when we all had to split, it was all but barren.
As you mentioned, we're looking for more people who can handle PHP. More specifically, we need people with a good sense of what makes a page look good as well as coders who can make that a reality. Taking a bare-bones mission entry form and making it look good is just as helpful as making that form in the first place.
So to sum up...
Interested poster and potential contributor, reporting in.
For setting up a formal list of tasks and user stories, I'd suggest Asana. I used it in the past for an opensource project started on my college campus, and it worked quite nicely.
As far as languages go, I'm partial to Python with Django personally. Though I have a heavy bias since this is what I use in the day job...
The list of features you've outlined here is excellent and would make for a good initial framework. Nicely done!
A spreadsheet does not lend itself well to a development plan. I've drawn up a Trello board here: https://trello.com/b/ICAylAE8/eve-missions
Let me know what you think.
Edit to add: I have versions 0.1 through 0.5 of how I think the development should step. Notice that stylesheet development doesn't occur until 0.5, as visuals can encompass a version release in their own right.