I'm late to the party and everyone else here has suggested how computer science experience can contribue to chemistry. I'm going to do a bit of that, but also point out how chemistry experience could potentially contribute to some (very select) CS opportunities.
I find myself in a similar position to you. I recently declared a double major in Chemistry and Applied Math-Comp.Sci emphasis because I enjoyed both subjects. I was initially planning to double in pure Comp. Sci., but our CS department is full of horrible lecturers and the math is full of amazing lecturers so I kinda got shoehorned into the other.
Computational chemistry is one of many fields in which CS and chem will overlap these days. It's not obvious, but there are many, many others, as people who are good with computers and science are rarer than they should be. Many labs, even those that are not computational in nature, rely on some basic modeling. I currently do some work with a nanoparticles group, and the PI was recently complaining that most of his grad students couldn't program anything to save their lives.
Failing that, our field could always use some good software devs. Perhaps I'm a little spoiled, but some our so-called "cutting edge" software suites have to be partially recomplied every time they are launched and suffer from spontaneously having communications modules crash, necessitating reboots of several computers in order to get things up and running again. It's pretty obvious to me that a lot of the stuff was designed by a software developer and not by a practicing scientist--such as the million button presses needed to load data and work with it, and the general recalcitrance of such software to spit out various data types.
If you don't want to work on that problem, we're still struggling with the issue of how to share code and models/data. Everything is moving to computers, and research is no exception. Researchers are still trying to figure out how to share files easily, store them, and publish them (more than one study has gone to press as a letter without any of the code attached to it).
Ultimately, I don't know what you want. Based off your last few paragraphs, this probably isn't what you were looking for, but since you opened with a question about the overlap between two fields, and not how one could contribute to the other, I'm leaving these here as ideas about how several fields can potentially interact.
P.S. For an interesting example, Philip Guo's PhD thesis revolved around the question of how the same code could give the same results when run on different systems, in spite of different environments. The question led him to create a tool (I believe Python) which allows simulations to run in a safely sandboxed (and thus identical) environement without loss of performance. http://www.pgbovine.net/PhD-memoir.htm