Sam Allen also did a workbench book worth checking out.
If you want to go through a semi-over-the-top woodworker
bench and the process of making it, with screws ups and
the way I fixed them - or made some into "features" check
out Das Bench - all 32 pages about it.
Or you can check out what is now a big assembly bench that
served as the only workbench for a couple of years - 1 1/8"
ply, 2x4s and a piece of 1/4" melamine.
Don't make it air craft carrier deck BIG - 24" wide is plenty
wide for most things and 6 feet long will probably work
for just about anything you want to do. If you intend to use
it to work with hand tools - planing, edge joining, cutting
dovetails, mortises etc. and handsawing up a storm keep it
low. Rule of thumb seems to be to stand up straight - hands
at your side, palms to the rear. Bend your wrist so your
palm is down and paralleling the floor-that's your bench \
height. Seems low but much of hand work involves using
your body weight pressing down.
GET YOUR VISE HARDWARE FIRST - THEN BUILD AROUND
If you go with long threaded rods to hold the legs to the
stretchers - get the Lee Valley "tension nuts" (see the
black "button" looking things on the end of this lathe
bench. Not that a routed dado in the back of the stretchers
for the threaded rod to sit in is easier to do than drilling
a really long hole through the length of the stretchers.
Unless you're blessed with a perfectly flat shop floor,
and if you don't care for shimming a leg, look into
leg levelers - preferably adjustable from above - with
an allen wrench.
Like the maxim - Buy Once, Cry Once - spend time
studying what a workbench can do and pick the features
that suit the type of work you do, or think you want to
do - then build ONE bench that'll serve your needs 'til
they pat you in the face with a shovel full of dirt and
the next guy gets to benefit from your bench.
A good workbench is an often overlooked but really handy
tool to have - clamps stuff, supports stuff while you work
on it, a place to pound, etc..