What he said. SketchUp has a learning curve like anything else, but it's free and it's reasonably intuitive to use.
A couple tips if never used it:
Don't even try without a mouse
Edit: I've seen people use SketchUp with a touch pad - I just find it extremely frustrating and slow.
Learn about groups and components and use them
Learn what all the main tools do right at the beginning - there aren't that many and the built in tooltips offer good descriptions of what each thing does.
Search the 3d warehouse before drawing anything complicated. Why spend a weekend modeling a toilet when somebody has already done it for you?