The short story is: use a font developemnet software package (such as Fontographer of FontLab) to build the TTFs and then either use ArcMap's Symbol Property Editor capabilities to build the symbols (not much fun if you are making a lot of symbols) or a VB program to put the symbols together (there are some samples in ArcObjects Online).
There are some "gotchas" you may encounter along the way, so the long story is contained in a one-day workshop that I have put together. I gave this at last year's UC in San Diego, but only five people opted to take it. It was well received, but because of the small attendance ESRI decided not to include it in the pre-conference workshops this year.
I would love to resurrect the workshop, however, getting enough interested people has been a real problem. I don't have any advertising budget and only try to recover costs with workshop fees. So right now it doesn't look like I will be able to offer this anytime soon.
I am in the middle of another project right now, but as soon as I have some time, I'll start working on a set of symbols for this type of use. There does seem to be some continuing interest in this. I will probably include circles broken into two through seven or more segments and I'll also probably experiment with star shapes (three-pointed stars, four-pointed stars, etc.).
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