There's alot of tutorials on the net and some may look very intimidating once you start looking at them, but keep in mind you may be looking at some advanced tutorials that are way out of many of our leagues. I personally recommend photoshop since it does everything but it's expensive and there is a fairly hard learning curve. But for me it was like I got kicked in the head and it all started to click, learning layers and blending modes was the trick.
I personally taught a friend whom had never used Photoshop before how to make an image in less than a hour with a template I made, we call them signatures on a message board, he returned the favor by giving me the latest copy of Photoshop complete of all programs for free, around 1,700 us.
like the others with drawing and scanning, I do most of mine cutting out a car and just using Photoshop and images I have of sky and grounds. Thereare some programs like GIMP, which I never tried but people do like it and I do believe it's free. Illustrator is tough also, i give these guys credit for this steep curve they went through.
Just grabbing a picture and using a programs filter can really make some cool stuff. Like HDR photos, line manipulations and so on. I prefer cutting out my image and then just brushing it and adding styles or gradients for colors and really manipulate the skies and grounds for effects.
I was hoping one day some of the guys would do a tutorial with screenshots of their programs also when they have time to show others, how relaxing and fun it can be.