If you are looking for some mathematical programming challenges either as exercises, smaller projects or just because you or students you know like mathematical puzzles than you will want to look at Project Euler.
Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.
The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.
There are 158 problems there when I checked and from the one line introductions some of them look like fun. There is probably something there for just about everyone.
[Found thanks to a link from Mark Punzalan a.k.a. “Punzki”]