Vintage action for Photoshop
I recommend using this action on a copy of the photo you want to add the effect to, because it will merge all the layers first.
The color effects are all in separate adjustment layers so they are very easy to edit.
How to use
Open a copy of the photo you want to use open the actions palette > load actions > locate the vintage action, hit ok > press play in the bottom of the layers palette.
Credits are welcome.
Update (dec. 2008):
This action has been featured in a videotutorial by Tutcast.com. Go check it out