What are good database/grade book software? I am in the market for a (hopefully free!) grade book software and  would like to see some suggestions. This would be used for a math class and I am planning for many grades (15+) per semester.

In particular, if a gradebook has any features that make it stand out from other gradebooks or spreadsheet solutions, I would appreciate knowing that information.
I'm guessing this question will get closed, but there are many options (as earthling highlighted in the comment). When I taught high school, I invested in Easy Grade Pro and was happy with it. It is not free.

Lately, I've been using a home-made Excel spreadsheet, which has been pretty easy to do, although I have a fair amount of experience with Excel. As F'x said, OpenOffice has a spreadsheet and it is free, and Google Docs also provide a free spreadsheet solution. You can also find pre-made Excel spreadsheets for grading, which you can tweak for your own use. 

Another option is to see if your school has a gradebook built-in to it's student-database system. This is a nice solution because you don't have to transfer grades from one system to another, and the students have easy access to grades along the way so they can explicitly track their own progress.