CompareDBs is a free tool for Windows that compares two SQL Server
database schemas and produces a side-by-side display of the
differences.

- Compare the tables and columns in two databases.
- Compare columns' data types, default values, maximum lengths, and
nullabilities.
- View a side-by-side display of the differences, or copy them to the
Clipboard.
- Smooth background execution with a progress bar.

You can download it here:
http://www.CL4.org/comp/comparedbs/