There's no single thread with all the information but you can find lots of tidbits if you scout around.
I'm in the oil business right now but hoping to break into capital markets next year. I'm weighing up Stern v Chicago, although I believe Wharton, Columbia and MIT would be good options as well. Anyway, I've done a lot of networking with current students and a lot of reading so I am happy to share what I've learnt but remember I'm no expert (yet!).
Key roles in IM are research and portfolio management. PM is very tough to get into for the uninitiated. IM firms do hire research analysts with no finance background but these spots too are pretty hard to come by, especially on the buy-side where you might have to recruit off-campus. Bigger firms like Fidelity and T Rowe Price have more regular recruiting needs whereas small funds hire ad hoc and closer to the summer. Sell-side research jobs are slightly more accessible (as a rule of thumb, sell-side recruits on campus, buy-side recruits from sellside).
To get in, have a love affair with the markets. Learn how to value companies and buy stocks. Know and understand your own portfolio and be able to justify your transactions. Everyone recommends "The Intelligent Investor" by Ben Graham, a former Columbia professor who taught, and later hired, Warren Buffett. If you're very green and this is too technical, start with Jim Cramer's "Real Money" then advance. If "The Intelligent Investor" is too simple, get "Security Analysis" by the same author. Also think about Bethany Mclean's "Smartest Guys in the Room" about Enron and "Liar's Poker". Also McKinsey do a great text on valuation which was recommended to me by a current student at Booth.
Next, read the WSJ every day. If you can, get the Economist too, and maybe Barron's and the New York Times. FT is good if you want to work in Europe. Also watch a lot of Bloomberg TV or CNBC (Squawk Box, Closing Bell, Mad Money). I know you have a job and a lot of this stuff airs during the day - I'm lucky and work in Europe so it's late evening when these shows are on and I can catch them online. If you're in the US get Tivo, or go to itunes and download the podcasts. This preparation should be interesting and exciting so if it's a chore, you might not be the right candidate for this career.
Also start networking with current students - it's not too early! Your school will have a finance club or IM club so email them and ask questions. But don't contact alums until you're a stock guru and sound like you know what you're talking about. Personally, I'm waiting till school starts for this.
The CFA is pretty useless for i-banking but it will help in any IM related career. The only difference is how much it will help! Big asset managers love it and if they hire you without it, they will probably expect you to get it done. Sellside may be a little less interested and many hedge funds reputedly don't care about it much at all. I'm taking L1 now, and it's hard work but pretty interesting. I'm planning to put in about 250 hours of study time. Volume is the enemy because there's a lot of material but you can compressed notes from Schweser or Stalla which helps a lot. MBA students report that it's possible to take the CFA alongside school, since there is a lot of overlap if your school's curriculum is finance-heavy. You should definitely register to take the test anyway because it shows committment to your cause (cost is $1000 or so) and you can put "CFA Candidate" on your resume. If you're employed full time it's too late to start for the L1 exam in June, but if you're leaving your job early and can start right now, you could certainly get the L1 test done before school. Pass rates are brutul (approx 40% for L1 and similar for L2, most people fail at least one of the exams).
Best of luck guys! Happy to take PMs if you want more info.