Rob, you can start here.
It's not the best example and the template it speaks of is a little bit out of date. You'll have to experiment by moving your icons around the canvas depending on your font baselines.
There's also this long post where he imports his vectors into FontLab. Drawbacks of FontLab are it's $649 price and it's learning curve is steeper than Inkscape. I also found FontLab to be buggy on my OS X install.
On a side note:
Someone needs to make software dedicated to this task...
