Try Popular Woodworking. They have some of the most accessible projects. For a really interesting/exciting small publishing company take a look at Lost Art Press. LAP is sort of the Pragmatic Programmers of the joinery world.

Accessible, indeed. PW makes things look so easy. I have a few projects on the TODO list thanks to them. Fine Woodworking has nice stuff, too, like this workbench: http://www.finewoodworking.com/item/18985/still-dont-have-a-....

If you're feeling adventurous, carry a tape measure and check out the size and shape of furniture around you.

If you really start getting in to designing furniture "The Measure of Man and Woman" (http://www.amazon.com/Measure-Man-Woman-Factors-Design/dp/04...) is full of useful measurements and ranges that tables and chairs should satisfy for average, 1 percentile, and 99 percentile humans.

Wood is actually pretty forgiving. You can prototype the size of something in cheap pine, and remember, it's always easier to cut off another inch from those table legs then it is to add one!

Woodworking magazines, woodworker supply shops, fine woodworking forums. Start digging around for what you're interested in and you'll find them.