I mean, I guess I could live without Photoshop, however I don't like to think about what that would be like. As an Instructional Designer, I write narration for my online courses, design interactions for my students to complete and build course structures for the courses to follow, however at some point the courses I design need to look like something. I rely on a mixture of stock photography, graphics that I dream up, and my own photography. One of the tricks I use is to ensure my images are in some way uniform, mostly in size but also in colour as well. It gives my designs a professional look and feel you don't usually see in the typical corporate PowerPoint training (I hate PowerPoint).
I found this Photoshop CS5 tutorial for beginners through the pop-up that shows up in Adobe Captivate and I thought I would share it. I haven't gone through it yet, but it looks pretty good. It contains over 13 hours of teaching material. Based on the topic list, which I scanned, it looks like I could learn a few things here and there.