I just found out about and it, I was browsing around and I found a website about linux versions of windows apps. One of the ones on the list was something called 'Sweet Home 3D', I clicked on it an it led me to the website. it looked like Google sketch-up(my favorite CAD program!) so it got me interested. I downloaded the Linux version, uncompressed it and ran it from the file.
The 'Sweet Home 3D' splash screen showed up and then it went into the program. One reason I was impressed was the fact that it 'just worked'(like Opera). Anyway, It's an interior design program with 2D and 3D views of your floor(there's one problem, you can't stack the floors!).
It's not as flexible as sketch-up, but in one aspect that is good, because it limits you to interior design and makes it easy to view. A clever program that I liked straight away!
I really think you should try this app if you have any interest in architecture or interior design.