If you have Photoshop, this would be pretty simple.
The loss of contrast and discoloration is done by creating a gradient on a layer and then setting that layer's opacity somewhere between 10% and 25%. Which colors you use in the gradient is up to you; most of the photos here are using warm colors like brown, orange, red, and yellow, though one photo looks to have a full spectrum.
There is slight vignetting in the very corners of the photos. This can easily be done using the Lens Distortion filter, or with more control by using other techniques (levels with masks, burning, multiply with masks, etc.)
Most of the photos also seem to have a slight cross-process effect, where darker areas have a blue tone and lighter areas have a yellow tone. Again, there are multiple ways to do this. My favorite way is to use a gradient map adjustment layer with the shadow end of the gradient set to blue and the highlight end set to yellow. Then set the blend mode to color and adjust opacity to taste; usually 10% to 35%.
The last photo with the big red spot is strange. This could be done by simply painting red on a layer in the area you want to affect and then setting the opacity to 60% or 70&.
