In the next few months I going to be producing more monochrome images, and after downloading a free trial of Silver Efex Pro, I ended up buying it. Long story short, this bit of software makes it easy to create a variety of black and white effects (it has over 20 preset effects, can simulate the effect of coloured filters and can emulate your favourite black and white film) and is a very good starting point for creating your own monochrome 'look'.
My only complaint is the plugins are not available for 64-bit versions of Photoshop at the time of writing (apparently 64-bit plugins are under development). Photoshop automatically installs both 32 and 64-bit versions on 64-bit systems. but it's a real waste of time having to do part of my post-processing in 64-bit and then having to close Photoshop and then open the 32-bit version... come on Nik!
*Can also be installed for Adobe Lightroom.