to
in 4 easy steps! Uses Curves and Selective Coloring. Done in PhotoShop CS2.
1) Layers > New Adjustment Layer > Curves
RGB: Input: 100
Output: 135 (Make this value lower if your image turned out too bright)
2) Layers > New Adjustment Layer > Selective Color
Reds: Cyan: -100
Yellow: +100
Black: +20
Yellows: Cyan: +100
Yellow: -70
Cyans: Cyan: +80
Yellow: -80
Neutrals: Cyan: +20
3) Layers > New Adjustment Layer > Curves
Red/Green: Input: 100
Output: 120
Blue: Input: 100
Output: 125
4) Layers > New Adjustment Layer > Hue/Saturation
Saturation: +15 (Depends on your image. Please increase the saturation responsibly. You don't want to end up with a grainy image)
And voila! Just tweak the Curves and the Selective Coloring until you're satisfied with what you've come up with. You can always add a Brightness/Contrast to give it a little bit of sprucing up.
PSD Other examples with little modifications: