As a graduate student I didn't get an opportunity to participate in a collaboration. We did work with other labs and we referred to those labs as collaborators, but for me they were just people who did my animal experiments. I don't consider that a true collaboration. In grad lab, we didn't even collaborate within the lab. Everyone worked on their own project, basically using the same techniques. There was a lot of open discussion and troubleshooting, but no collaboration.
The lab members in my post-doc lab come from pretty diverse backgrounds, including microbiology, biochemistry, immunology, pediatrics and structural biology. One of my small projects is a collaboration with a structural biologist. Structural biology is not my favorite topic, nor is it my strong suit, so I was curious as to and how the collaboration might progress. As it turns out, the structural biologist actually knows less about my field, than I know about structural biology, but somehow our skills are quite complementary and we work well together. I came up with a few good ideas to solve a current problem we are having and I presented them to the structural biologist, who after getting over his/her surprise that bacteria could in fact do what I was proposing, built on the idea, making it much more interesting. The final product was a pretty good idea that neither of us would have come up with on our own. Of course, there is always the possibility that it may not work.
So, although it's just a small collaboration and with someone within my lab, I am pretty excited and looking forward to collaborating more in the future.