On our website we record thousands of events in tables each with a unique timestamp. Is there a tool that can plot for me the number of timestamps that fall within a day, week, or month, on a graph a-la-google analytics, to help me understand the trends?
If you want a simple graphing tool, take a look at Graphite.
If you on the other hand want do do complex analysis, you would best use some sort of OLAP tool. I personally know Pentaho a little bit, which is an open source business analytics tool.
Finally, within the Pentaho dashboard you'll find the Marketplace, where you can install open source tools to create dashboards or create dynamic queries via the Saiku-UI
I realize this is not your click-and-go solution, but in the long run you will get a lot more value out of this solution than a simple graphing tool.
Since the data is already stored in a SQL database, you might look at SQL Reporting Services. It's not difficult to get it up and running, though a little coding knowledge will go a long way here.
This article gives an example very similar to your dataset: