Hemlawk, that first pic has a lot of potential. It's not a bad photo, it just needs to get a bit more thought. For instance, I would move left a little bit and change the angle, see more of the badge and grille and less of the background. Move the second car close and use it as a secondary subject also. Right now it looks kinda like it's just... there. Maybe move it closer, pull it forward and get a good shot of the rims in there? Or pull it perpendicular and use it's grille also as a background?
The second picture is just a "snap shot" it says "hey, here's the back end of my two cars." Now, take the same two cars... drive to a nice background (lake, mountains, industrial area etc.) park them at an angle and get lower to the ground... most photos of cars you want to get lower - it gives them a great presence.
Look online for some guides or just general information on composition, the rule of thirds, picking a subject, etc. Heck, google "what makes a good photo" or something like that. Keep in mind though, background plays just as much of a role as your subject does.
As an example, which of the two below do you think looks better? This was an experiment in lighting for me using glass and wood flooring (read: my dining room and table
). Notice the first one is just a snap shot "hey, look at my junk." But the second one has more thought, isolation of the subject, awareness of the background and proper lighting.
PB3, Adobe Photoshop - bar none. But, there are other programs that are free. Gimp is a good one if memory serves. I've just been in PS for years so I'm so used to it I can't adjust to anything else.