There are many class libraries available under free licenses for producing graphs and datalogging. I have found the ZedGraph library to be extremely powerful, and reliable. Below is an example of the kind of work I have acheived using it. This section will give a breif tutorial on how to produce basic graphs using the ZedGraph library. (http://www.zedgraph.org/) It will then continue with techniques for logging and storing data inside a MS Access database.
The above example samples data using the serial port, stores the data inside an access database and plots this with the ZedGraph libraries.