These are renders of my snowman and sci-fi crate from the core mesh modeling course.

Thank you. I've been trying to learn Blender for so long, but I've made little progress. I'll keep trying!
A rendering of my soccer ball from the core mesh modeling course. I added some low-poly assets to the scene. They don't match the ball, but I wanted to add something else to the scene.

Here is a render of my hard drive. Just for kicks, I added text to make it like an advertisement. I'm also trying to learn some graphic design applications.
I couldn't do this on my own. I tried to model it in one piece. The most significant lessons that I've learned here are that non-manifold models are not only all right, but that they are preferrable in certain cases, and that at least in hard-surface modeling, N-gons aren't necessarily bad.

I ran into a small problem at the end. After adding a cylinder to make the legs, the cylinder's vertices decreased when I tried to rescale it. I'd applied the scale before doing so, and the only modifiers that were added were the "mirror" and "smooth by angle" modifiers. When I duplicated a face from the cylinder to make the feet, I got fewer vertices again, and when I rescaled the bottom of the extruded feet, I got even fewer vertices:

I'll keep messing around to try to figure out what went wrong, but if anyone has any insight into this, I'd appreciate your advice. Thank you, and Happy Holidays!
I spent too much time making this, but I really want to apply everything that I'm learning, so I made some more dishes in addition to the coffee mug. My children found it very amusing.

Here is my CG Cookie cookie. I had to restart it because I made the mistake of connecting vertices with the fill face command and I got my normals every which way. I wasn't able to achieve perfect quad topology, but I kept the tris to three, and I used one of them to furrow the cookie's brow. Anyway, the perfect topology that I see in character models seems very far from my grasp at this point, but I learned a lot and I'll keep working at it.

It's looking great, Derek!
Topology is complicated and it's not just a matter of Quads being better than Triangles (or N-Gons). Just a simple example, I'd say, that in most cases,the Triangle in this image is 'better' than the three Quads:

And often, in flat, non-deforming surfaces, Triangles and N-Gons are totally fine.
Thank you. It's just that I know that with better planning, the topology would have been cleaner. I probably defined each shape more finely than I needed to, so then I had to add more loop cuts to keep things aligned and to try to maintain a flow, a flow that I eventually had to break in places. I could have fine-tuned more basic shapes after filling out the topology--as in the tutorial--instead of trying to get the shapes right in the beginning. In drawing, you sketch out a scene using very basic shapes in order to get proportions and perspectives right before moving onto finer details. 3D modeling seems to be similar in that way.