I do a lot of this, most often I get a lot of joy from this free Photoshop action which can be downloaded from here:

http://www.digidaan.nl/indexframedigidaan.html?channelmixer/index.html

Worth checking out if you like a lot of adjustability. Add a nice duotone or colour filter and it's looking great.

Oh yeah...

A *great* free plugin is

http://www.optikvervelabs.com/

With loads of preset filters emulating classic film and camera types, in both colour and black and white, all fully customisable with sliders.