momentum - Where can I find the equations for "quasi" elastic collisions?

Yes, you all talk about neutrinos and spins, but I came out with this basic s**t :D

All of us learnt the basic equations of collisions, elastic (everything bounces and energy remains the same), or non-elastic (the classic example where objects remain stick together). What if objects don't remain together and some energy is lost (a fraction of the kinetic energy of course)? I tried to solve the maths and since I'm just a Java programmer, I realized that after 6 years away from University I can only do 2+2 and little more. Apart from joking, the equations come out as a system with an elliptic curve (for energys) and a line (for momentums). Anyway I'd like to get a solution that is good enough to do some analisys over initial speeds, energys and so on.

Please don't flame me, probably my english for physics is not exact, I studied physics in Italian and my everyday bread is IT.

Thanks