Some ideas to ruminate on.
With you as the guest in another department, thoughts are:
- $\LaTeX$ presented to a writing class, preferably one where they've already had to submit three or more papers that were graded on presentation as well as English usage
- Web design (for portfolio usage maybe) to any arts or photography class
- Mathematica, if available, to any advanced mathematics or lab sciences class
- SQL (any flavor) to any business-related classes, if any exist at your school
At these engagements you can show how the program can be used in real-world application to what they are learning, and/or be useful to them in their class now. Best of breed for that would be the use of $\LaTeX$ for the writing class - freeing them from formatting and presentation details to work on their writing skills
As a guest in the computer class, you could look for any instructors that rely on computer programs in their course material. Especially useful would be any that employ a program that is Free/OpenSource software. (If it is hosted on GitHub where they can also look at, that's even better.) A good candidate might be an art class that uses GIMP.
If you find a significant portion of your students have a common interest in another field, you could engage that department for a collaborator who can show how the computer is used in their field, even if it's not applied in the classroom itself. (Of course that could also include teaching those instructors as well, so that they are in a position to understand the tools at least as well and the students they teach.)
Lastly, to get things rolling, you could offer to do a session or two in another class to teach their students extra features of the Office software that they use, if any, with the students. Lab science classes probably need at least Excel for processing and presenting measurement data from experiments.
The first set of ideas is to present how the use of computers can help them now with their classwork. The second set is to show your students the application of what they are learning in your class to things they already know, or will be taking soon. The third set of ideas shows how computers are being used in the work-a-day world to make things easier, or better, in the field they are really interested in. The final idea is a method of beginning the idea of collaboration in your school before the other instructors realize it's even possible.