wow you are ambitious. have you visited one or more of these schools? this may give a good idea. some schools are more geared towards computer generated work. i have no experience with any of these schools, but when i applied to architecture school, there was no portfolio requirement for the first year, which was pre-architecture. after this first year of pre-architecture, then we submitted portfolios to stay in the program. maybe they don't do it this way anymore. anyone have more input to add? i am not sure if there is a website like you asked but there probably is. i would think that any of these schools has something to offer to a prospective students if you ask for it.
anyways, if you are in high school, take art classes, photography, visual arts, you can take some courses at a local college to start on college credit if you can. extra credits will help and getting the college experience early is good. take classes that will be likely to transfer and that aren't too difficult. i remember when i applied, they weren't looking for the ready-made know-it-all architect, but rather students with diverse ranges of interests and talents that were ready to take on the challenge architecture school offers.
sounds like you have a drive for sucess!

i can tell you for one thing, Cooper Union will have you complete a home test and that will make up most of your portfolio. as for the home test, it is typically amazing questions that ask you to respond in a graphic fashion. oh and the test is typically different each year.

i applied and got into risd and carnegie. Although they are both great schools they are on different ends of the spectrum...RISD is a top notch art school whereas CMU is great for computer science and engineering. However they both have great architecture and ID programs but go about teaching these programs differently. The first year at risd is an art boot camp compared to CMU where you take calculus or other non art classes. As far as portfolios go...CMU doesnt even require a portfolio for admission into the architectue department. They will even act like they dont want it...WTF? Send one anyway...it will help you satnd out...remember colleges are looking for students who have special abilities and talents. Furthermore i got into carnegie over my friend who had way better grades then me. With RISD the portfolio is a very important aspect for admission...THe RISD reps. at portfolio day were ass holes to me and i felt like i wasnt going to get in. I did...and after being here for for a year i know i didnt "just" make the cut and am a lot better than those reps lead me to believe. Furthermore students have strengths in different areas...some kids cant even draw but they may be amazing photographers or ceramics majors. So basically your portfolio should reflect your interests and if you have talent you should get in. As far as Cooper uNion's concerned i didnt even mess with that. Their home test is pretty ridiculous but hey the school is free if you get in, even though NYC is a shitload of money. I love Risd and and am glad im here. The school has a real intense atmosphere and once you get into their arch program you learn sooo much. Its also great to have classes with the grad students as they always bring different perspectives to the table. I could go on and on but dont want to sound like a pansy gloating about their school. All of the schools your aiming for are great you just need to find the one that fits you.

wow thanks so much for the comments. i really appreciate it!