Shiny- Once upon a time I took a photography class, but honestly that has been so long ago. I remember going over lens and ratings but I think (long ago) that we did it on film cameras.
I can kinda relate to that; when I first learned about this stuff I was shooting with my dad's old Canon AE-1 Program, which was a 35mm SLR with no auto-focus. It did have auto exposure and automatic shutter speed settings, but for the most part it was a manual camera. A lot of the basic principles are still the same now, but the technology backing it up has changed drastically.
In your pictures the background is out of focus, is this a function of the lens or the FS you had the camera set on? What would be the FS of a standard 18-55 lens? Or does it vary depending on the zoom?
What you're seeing is a "bokeh" effect, which is largely lens-dependent. A larger aperture lens makes this easier to achieve, and in the case of the 50mm prime lenses the optics provide very crisp and clear transitions between the in-focus object and the out-of-focus foreground or background.
All it really comes down to is playing with depth of field, and for that the larger the aperture (FS), the shallower the DOF. That's why I like shooting in aperture-priority, it gives me control over DOF and lets the camera worry about the rest.
For a kit lens like your 18-55m the range is f/3.5-5.6 (3.5 is the largest aperture through the middle of the focal range, 5.6 is the largest from mid-range to the highest focal length) which will give you decent bokeh in some situations, but it's not ideal for creating those kinds of shots at all. If you want a lens with a consistent aperture throughout its focal range (speaking in terms of zoom/telephoto lenses), an "L" type lens would be needed. Those are much more expensive, though.
Here's a video I found that kind of demonstrates what I'm describing:
[ame=http://www.youtube.com/watch?v=uRJMisfK_-Q]What is Bokeh? - YouTube[/ame]