I mentioned my Excel thing in the "What are you currently reading?" thread and thought I'd share it with you folks here. Maybe someone will find it useful. The hardcore book geeks I'm attaching it to this post. I hope this isn't against any rules.
To use it you need to have Microsoft Excel. In the attached ZIP I've included a file for the 2007 version, as well as another one compatible with the pre-2007 versions. It's a sample containing two entries, which you'll have to modify as per yourself, obviously. As you enter your data Excel will show you how long it took you to read each book, and your average pages read per day. There will also be a running overall average, as well as total pages read. All in all, it's rather simple and self-explanatory.
Any questions, feel free to ask and demand any adjustments or enhancements
P.S.: Just a quick tip. The best way to start entering your own data is to select the entire Row 4 by mousing over the row marker on the left and clicking it. Then inserting however many new rows you need. Then select the first book row (Row 3), copy it, and paste that all through your rows. Then enter your changes. The data should update accordingly by itself.