What can I do to help put the "spark" back in our relationship?

My girlfriend and I have been dating for almost 2 years now and we've had our share of problems, but over the last few months we have been doing very well as far as getting along with each other.

Well recently it seems like we can't hold a conversation for very long and we seem to be getting short with each other and the affection between us seems to be very very minimal. We both love each other very much and want our relationship to work.

Is there anything I can do to help get that "spark" back that we had at the beginning of our relationship?