a lot of folks use smartdraw:
smartdraw
I prefer Visio which unfortunately was acquired by Microsoft:
Visio
I like Visio for three reasons.
1) its not that expensive, and its a professional piece of software, not shareware or freeware with loads of bugs.
2) it has an extensive drag-and-drop library. Want a bathroom over here? Drag off the walls, toilet, sink, et al, and toss it where you want it.
3) you can make your
own libraries. So anything you draw and like, whether it be a room, partial structure, a fixture, etc, you can save them into a library, and its fairly easy to do.
I have yet to need more than the online help on rare occasions.
I have all my studio equipment in one library, top view for floorplans, and front view, for rack documentation and the like.
Hope that helps.
BTW, if neither program works for you, there is mucho freeware and shareware out there that probably could do the job with a little more effort.