Start with http://en.wikipedia.org/wiki/Discrete_mathematics

Sprinkle in some cryptography for interest.

Remind them that some problems (e.g. in queueing) are most easily solved with non-discrete maths.

Data Warehousing is an application, better taught by an IS practitioner than a Mathematician.

for IT students requires all most all topics in discrete mathematics, especially

1. number theory

2. recurrence relations

3. mathematical logic and logical circuits

4. group theory, rings and fields