1. I use AWStats.
This means that I run a logfile analyzer over the webserver's logfiles and aggregate some statistics from them. I can determine your operating system and browser choice as your browser reports them and with your IP address, I can identify the country your ISP is hosted in. I also use the AWStats miscellaneous tracker which also lets me know your screen size and which of certain browser plugins you have available. AWStats also sets a cookie on your system that lets me know if you are a new visitor or a returning visitor and also lets me track your path through the site. This information is not tied to any individual person as the data collected is not enough to identify a single person.
2. I use Google Analytics.
I don't know precisely what they track, or how the track it. They say that a cookie is used and that no personally identifiable information is collected and who am I to suggest otherwise ?
3. I use the MyBlogLog tracker.
This one is new to me but it seems to track much the same stuff as Google Analytics. If you are logged in to MyBlogLog when you read my site, they will know and you will appear on the recent readers list. The advantage for me is the community involvement. Presumably, as part of the community mentioned in the previous sentence, you derive some benefit also.
4. The middle name guesser.
The middle name guesser is storing what would appear to be personally identifiable information but isn't. When you help the middle name guesser to learn, it stores your first, middle and last names. It stores them so that there is a link between your first and middle and your last and middle names but no link between your first and last names. This means that even someone who had access to the entire database could only figure out your full name if your middle name was unique in the database. This is also true for your parent's names. Each part of their names are only connected to your middle name and not to any other part of their name nor their partner's name. It would only be possible to determine their names if your middle name was unique in the database.
5. How I use the information.
Currently, I only use this information for analysing my site's visitor's behaviour. This helps me to focus on what you like and fix up what you don't like so much. I am the only person with access to this information. The data collected by the middle name guesser is only used for increasing the accuracy of the middle name guesser.