I have a C# application that creates a nice graph of the data that the Arduino sends it, and stores it in a database. If you are interested in a copy, PM me.
I have been logging temperatures from one of my projects for about 2 years now. ( 10 temps once every second)
I use the wonderful RRDtool on linux to log the temps as that way I always know the output size, and once you have figured out how to... it makes nice graphs.