Does there happen to be a free program on the internet that allows you to design a house?

I am 13 years old, and really interested in designing houses (like rooms and stuff). I want to know if there is a program to let you design a house, that is free, or has a free trial version...?

Public Comments

1. Google Sketchup http://sketchup.google.com/product_suf.html it is completly free.
2. Sketchup's good, but if you're not doing this for any professional purposes, there's always The Sims.