OK, here is everything you need to know to jump start your research (version 3.0)
In this forum when you are looking at the threads, left click the word views and you will get a list of the most viewed threads.
There you will find a dozen or so well documented build threads that you can read beginning to end.
the fact that there are a lot of views means the thread was active a long time with lots of documentation and pictures.
Don't overlook Chinadogs photo album on Flikr were he has over 1000 pics of HT construction details. The link is in his thread.
My favorite pictorial reference is an old build by Kirk who did a DIY but professionally designed theater by Dennis Erskine. his photo documentation is here:
At the top of this section of the forum there is a sticky thread "master show me thread" be sure to check out those linked threads for ideas:
Also in the sticky threads is a riser height calculator that everyone should use to get a second opinion.
Next you can read everything you need to know about soundproofing from the library of articles on the website of The Soundproofingcompany. Yes they sell product but the background knowledge is right on target.
When it comes to projector issues your best bet is you hang out in the projector discussion threads. If you don't see your question answered ask a question. Read about the new projectors from Sony, JVC, Panasonic, Epson.
There are on-line projector calculators to help with determining the proper distance and setup.
sample interactive calculator: (click the icon for the projector calculator, bottom left)
That site also has a lot of background info on all the terms and issues you need to be aware of when selecting a projector.
When pulling out the checkbook: Don't buy chairs locally. We will hook you up with super deals from internet dealers who hang out on the forum all the time.
Give AVS a shout and let them compete for your dollar when you get ready to buy your gear.
One fellow AVS builder (CJO) summarized a lot of the resources/links he used in his thread this is a very impressive resource and should not be missed: