What are the best tools for doing reports on your data?

Like many of you, we track a lot of things in our startup, from analytics to the internal business processes. However, periodically we'd like to see other more detailed events for sanity or cross checking, in a report-type fashion. This is the kind of thing that Excel would do nicely, after extracting from our DB (MySQL, via csv), but that's a pain to do periodically. We'd like to see things like a graph of events of type X per day, or per day of the week, or per week, for a certain period. What tools do you use for these?