SQLRaptor is a MSSQL compare and documentation tool.
It is constituted of two tools: a documentation tool and a compare tool.
Essentially the documentation tool, uses SQL-DMO calls and ad-hoc queries to reverse engineer your database, and then places all of the documentation in a HTMLHelp file (.chm), or in a RTF file or in a website. You can even add your comments to tables, columns, views and stored proceures directly from the HTML generated (see add comments to DB objects section in the manual).