Thanks to all of you for your suggestions. Kickhaha, I think I recall you recommending OmniGraffle once before (when I was trying to draw a plan for how the different parts and pieces of my editing gear connect), and I got it... thought it looked great... but struggled with it. I confess I'm not patient. I just reopened it now, and drew a room outline and a wall. But then I looked everywhere to have it draw on a “graph paper” background, and couldn't find it; neither could I see how to get it to measure in feet and inches instead of centimetres. Arghhh! I'm sure it's simple, and I just can't see it.
ezkcdude - - same thing happened to me with Sketchup. (my ego's really taking a beating tonight).
Gargoyle, I liked the look of the jordan on-line planner... very neat, actually (and easy to use) - - I'm going to test it out. (what's the downside, I wonder - - are they going to bombard me with advertising?).
Lastly, pscates2.0 - - this one looks really good... (and actually, there's a slightly cheaper version $150 instead of $250, that, I'm sure, would do more than I need). It seems the company doesn't let you demo it (problem for me - - what if I can't convert from metres to feet!!!?). I've emailed the company to ask if I can try it out somehow - - if they let me try it, and if it's good, I'll let you know.
Thanks again everyone.