I like your shots a lot! You're certainly beyond the beginner stage!
Anyway, I'll throw out a little constructive criticism. It CERTAINLY doesn't mean these are bad pictures (they're quite good) but without critique, how will you ever get better?
On the first, you've got a great concept. The silouette is ALMOST perfectly exposed, though the highlights on the cross are blown out slightly. Digital cameras tend to overexpose, so if you underexpose slightly, you're more likely to get a usable image (which you can lighten later and still retain all the detail). The cross seems slightly out of focus. Perhaps a smaller aperture with a longer exposure would get it all in focus. That's where a tripod would come in handy! Finally, and worst of all, the horizon is tilted! Luckily it's a very easy fix, just rotate it slightly and crop off the edges. Fixing the orientation would be the easiest and biggest fix to this photo.
The second is very well composed, but it seems that the top -- especially the top right is wasted space. I like the lines of the slide though. Perhaps you can crop off the top and sides to get a more powerful image? It's always more powerful to get a subject moving INTO the picture rather than out of it. If you took this shot again, perhaps you could tilt the camera vertically, then capture the lower end of the slide rather than the top.
I absolutely LOVE the lines in your third! Particularly the way the path moves into focus and how the power lines disappear into the distance. However, it's tilted slightly like the first. Straighten the horizontal and vertical lines, and it'd be worth keeping. Also, I almost feel like there's too much empty space in the top half of the picture. Perhaps you could play with cropping off the second tier of trees (in the distance). I think it would emphasize the people instead of drawing the eye up to the promenant forest.
Finally, you've got an amazing football shot! I imagine it took you dozens of tries to get something like this -- that is unless you're MUCH better than I at catching those perfect moments

The only thing I'd try to do in the future is to use a wider aperture to throw the background more out of focus. In the priority modes, you can either fix a wide aperture or fix a shutter speed that GIVES a wide aperture. Also the more zoom you use, the more the background will be thrown out of focus. As it is it competes with the football players where a defocused background might help them pop out more.
Again, your shots are great, and certainly better than most of mine! I just really appreciate it when people tell me how my photos could be better, so I thought I'd pass along the favor