what I really need is called a "half-wall" with a counter top.
I also have hardwood floors so I would like it if I can install this without really damaging them in case I want to remove the wall at some later date.
If you build a simple 2x4 wall and screw it to the floor, I'm betting it'll fall over the first time someone leans on it.
You can strengthen the wall by fastening one end to a stud in an adjoining wall. But the free end will still swing around.
If you can add an "L" to the end and fasten this to the floor, you'll gain a lot of stability.
Increasing the thickness of the wall can help. For example, build the wall with 2x6's or 2x8's and screw the base to the floor on the outside edges. This will give you a little extra leverage. But, you'll probably need to cover one or both sides with plywood to keep the studs from simply pulling away from the base. Also, be sure you are screwing down through the floor and into the floor joists below. Screwing into the wood flooring won't be strong enough.
If you have enough room, you could install a narrow cabinet instead of a wall, and put the counter on top. You'll gain a little extra storage in the process.
In fact, you could even put casters on the bottom of the cabinets and hide them behind baseboard trim. You wouldn't have to make any attachment to the floor, and could move the wall around when needed. A local chinese restaurant uses walls like these, and they seem to work well.
Anthony