This instructable is organized as follows:
Research and Design
We're building our own table, whether because we're tired of tables that aren't quite right, we have a space that no table on froogle will fit, or we just always wanted our very own kickass table that no one else has.
The premise here is that you'll be building from standard lumber from somewhere like Home Depot, that you might not have a garage, that you haven't built furniture before, and that you haven't worked with any wood longer than 12" before. All of these were true for me. The only requirement is maybe that you aren't afraid to deal with arithmetic in units of inches and 1/16-inches, and you enjoy thinking in 3D. If instead you want to work with recycled lumber, consult these excellent instructables here and here, but hopefully this instructable can still help you with planning.
In regards to time commitment, research and design took about the same amount of time as planning, while actual construction probably took only half of that. In my case I did the thinking and researching over a week, and then actually got the lumber and built everything over a weekend.