There are several, but
this seems to one of the better ones, and I believe that it's free.
There are are a few threads
here and
here that you may want to read, there's been several threads that have discussed logs and diabetes, they may be helpful to you, try searching for diabetes and you'll find many more that can provide more guidance for you.
Good luck, if it's you that needs to track, control is very important, both my wife and daughter are Type 1, and test several times daily, and log everything.
There's also newer meters that keep the readings and can be downloaded to a PC.
Gary