Be sure to trim, crop your photos so that they dont exceed 1000 points in any direction, like you did in your last photo, when posting here.
As for the pics, remember that as a rule of thumb the lower the ISO and the lower the amount of time(Tv) you use, the less noise/grain your photos will have. And also be sure to expose correctly, because underexposure also causes grain.
I see you are new to "real" photography and are only just learning to use manual, which is very good because M mode is the best mode to use if you want "perfect" or great photos, specially with long exposures. Also, remember, You are more intelligent than your camera, so don't let her choose settings if you can.
What mode did you use to shoot these pictures?
Thanks for your contribution.
I uploaded these pics using photobucket. I resized them to 1024x768 and for whatever reason, they change back moments later (sometimes, the one of "my tree" stayed... The pic of my Jetta was taken at ISO800, f/2.8 for 15 seconds. According to my light meter, it was about 1 stop underexposed. My options were to take the picture and deal with it, or raise the ISO to an even noisier level.
What I have been doing is putting the camera in M, leaving the light metering at "Evaluative", setting my f-stop and then press the * button to allow the camera to set the exposure time for me, all while leaving my exposure compensation knob at 0. In this case, turning the exposure knob to +1 (thus adding to my underexposed photo) did nothing as the f-stop was already as low as can be, and the exposure was already at a max of 15 seconds. I just ordered the manual shutter release from Amazon - hope it allows me to go beyond 15 seconds!