I JUST finished building one myself. I started a similar thread a while back for the same info. I looked at LOTS of plans for purchase (too complicated) and other people's ideas and finally decided to take what I liked from all of them and plan it myself. A few of the things I looked at were:
Most benches are made for using a stool but my back won't handle that at all.
I had a fairly large area to use and didn't want to be reduced to someone elses size.
I wanted to "mount" numerous presses etc. but also wanted a large clear area for home smithing (read messing up a gun).
My final build comprised of three 3/4" sheets of plywood, 2 4x4's, lots of wood screws, and a bottle of glue.
I cut the three sheets of plywood to 30" X 72". I had just over 6' between a pegboard and an open door, and I wanted about 22" of working depth plus room to put a 8" shelf unit at the back of the bench. Then I decided how high I wanted the TOP of the bench and subtracted 2 1/4" (the thickness of 3 pieces of plywood) mine was about 27". Then I cut one of the 4x4's to just under 6' and lag bolted it to the wall at 27" and cut 2 27" legs out of the other one. On top of this I mounted the first piece of plywood. Out of the next 2 pieces I made 3 dove tail openings where I wanted to mount components, one near each corner and a third close enough to one of the others to use as a gun cleaning rack. The dove-tail was a larger opening in the middle sheet (about 14x12) with a smaller opening in the top sheet (about 8x10). I mounted the top two sheets of plywood together with LOTS of wood glue and LOTS af screws (enough glue to squeeze out all over and a screw every 6-8"). I then made 9 dove tail inserts, 3 blanks to create a flat countertop surface, 2 as a gun cleaning rack, one for a Rockchucker press, 2 for shotshell presses, 1 for a powder thrower. Then I made a 36"H X 72"W shelf unit for the back of the bench with a pegboard backing for all(some) of my STUFF. Any of this can be adapted to fit your area, needs, size, etc.
Since the dove tail inserts were made of the same wood as the bench I took a router and removed about 1/64" of wood from the bottom of the dove tail area so the insert could slide in and out. I could have used sandpaper or sanded the insert instead but I like power tools OH-OH-OH.
Since my woodworking skills are less than great the dovetail inserts don't fit TIGHT. I haven't resized large cases yet to see how it works but if it is too loose I will figure some way to tighten it up if needed.
I hope that this is at least as clear as mud. If anyone has questions please ask, or if ANYONE would like pics e-mailed I would be glad to take some and send them, just let me know your address. Life is too crazy right now for me to try to figure out how to post pics here, sorry.
Good luck with your project.