Here are my sources (here were Meryl's):
Experience. I'm a handyman, I used to work for a tile setter, on a paint crew, and even for an electrician for a short period of time, so I've gotten to help enough people over the years to do a decent number of these things before. I've learned from my mistakes and the mistakes of those I've worked with.
Community College. I've taken a few carpentry classes at the local community college. I've also taken a plumbing course, two courses on residential electricity and a class on solar panel installation. Trade schools and community colleges are a great resource. They're cheap and put you in direct contact with professionals in the field - pros who are taking courses to further their career, as well as semi-retired contractors who now teach the next generation of tradespeople.
Magazines and books. Anything that the Taunton Press puts out is reliable and worthwhile. I have a ridiculous number of books from them and other publishers on everything from trim and roofing to furniture building and built-ins. I also subscribe to Fine Woodworking and Fine Homebuilding which are both published by Taunton Press. Other magazines I subscribe to which provide good information: JLC, Wood, Family Handyman, This Old House and (to a lesser extent) Popular Mechanics. For code information I go with the great Code Check series of books and manuals.
TV. This Old House is where it all started for me. They've been there forever. I can't say enough about Norm and Tom and the rest of the crew. They're an inspiration and the whole TOH franchise is a fountain of information. Other shows can also give occasionally good information, but none are as good as TOH. Holmes on Homes and Hometime are two of the better also-rans, but aren't as reliable or informative as TOH in my opinion.
Internet. I also frequent a contractor-only forum online which has a lot of info from people who are out in the field more often than I am. These are real pros who work every day, often doing the same stuff day in and day out. That kind of experience is invaluable.
Just as important as sources that you can trust are sources you can't trust. Youtube and ehow are examples of websites that occasionally provide useful information, but can't (in my opinion) be trusted on a consistent basis. The internet is full of people who are figuring stuff out as they go. There's nothing wrong with that, but it's not nearly as reliable as following the lead of professionals who do this day in and day out.