I'm trying to write a program that generates a bike fit for a person based on the data they plug in.

I'm finding it difficult to find formulae on hybrid bikes and mountain bikes. And also information on the differene between a female and a male fit.

Any suggestions/formulae?

I don't think it's possible to make a 'perfect' formula, different companies measure their bikes in different ways. Better to check the fit for each individual bike to their standards

You also need to factor in the rider's flexibility. Stem reach and rise are very personal, and really can't be left to a computer.

There's already a program out there that exists that does this. I saw it, and it does take into account flexibility. Dunno what the name of the program is, but this dude used it when I went to his shop and got measured for my bike.

Koffee

There are 2 separate things that you need. One is a mathematical equation which can convert body dimensions into bike-geometry layout. The other are some variable factors that you can use to tune the equation. Factors such as the back angle (upright/touring/racing), and knee-over-pedal spindle(offset thereoff), and rider's rotation about the BB (forward, or layed back). You can work out what factors you need for different types of rider.
There is no big difference between MTB, hybrid and road, apart from these types of factors.
As an intermediate stage, you want to get a set of points of contact, in X and Y. The origin may be the bottom bracket or the pedal at 3:00.
Once you know where the pedals/saddle/bars are, you can set the bottom bracket height, seat angle, axle positions, and aportion the length between stem and top tube.
Dont forget to make crank length proportional to something (femur length?), and that they are available in sizes from 140-190mm, not just 165-175.

Have you seen Peter White's fitting guide?