There's a number of programs out there that are designed for that sort of thing, but I don't know of any free ones (then again i haven't gone looking). I know there's a site out there that offers a service where you can send them a scan and they'll turn the letters into a font for you too.

That having been said, there's another option, if you have adobe illustrator you can use it to do a live trace of a scan where you have your letters drawn out, that might be the fastest way. If you don't already have AI, you can use Inkscape, which is a free version of same, but I don't know if it can do automatic tracing. Might take a bit longer to trace it all out by hand, but it should be doable. I imagine at that point there would be a program that can import vectors and output them as fonts, but I'm just guessing at this stage since I've never really looked into doing that sort of thing.

I'd go looking right now, but I'm on a roll with my current map (just taking time out while waiting for it to save to check on the forums, heh. it's gotten large enough that it takes a few mins to fully save, whee!)