I have a non-Apple keyboard that doesn't have volume buttons of any kind, yet I find the ability to change the volume from the keyboard incredibly convenient. System Properties' built-in keyboard shortcut manager doesn't support global shortcuts (I want to be able to change volume no matter what application is active), so I went in search of a solution and found Spark, which fits the bill nicely. Coupled with a few Applescript scripts, I've got volume control tied to some function keys.
For those who need help with Applescript, simply open Script Editor (Applications > Applescript > Script Editor) where you can paste in those scripts to test them. Alternatively, just save each one (minus the function definition) into files ending with ".scpt" and they will then open with Script Editor.
Good news. I broke my apple keyboard and can't afford to buy a new one right now.