Here are some useful addins I found for SSMS 2005/2008 on CodePlex and thought of sharing it with my readers.
Internals Viewer for SQL Server - Internals Viewer is a tool for looking into the SQL Server storage engine and seeing how data is physically allocated, organised and stored.
DataScripter - This Addin for SQL Server Management Studio 2008 allows you to generate INSERT statements for all values of a table easily. Just select Script Data as from the context menu of the table and choose one of the options
Fulltext Management for SQL Server - This Addin for SQL Server Management Studio allows you to manage your fulltext catalogs easily. It even works for SQL Server Express editions, so now you can use a nice GUI instead of unhandy SQL commands.
SQL Compact data and schema script utility - This console app and SQL Server 2008 Management Studio add-in helps you better manage your SQL Compact development efforts. If allows you to script schema and data to a .sql file, which can be used in any context. It also scripts DML for use in SSMS scripts
SQL Server 2008 Extended Events SSMS Addin - SQL 2008 Extended Events are a powerful new way of troubleshooting problems with SQL Server. One short coming is that there is no UI support for this new feature. The Extended Events Manager is a SSMS Addin to bridge this gap.
These were just a few of the many addins created for SQL Server Management Studio. If you know of any other addins you have used, please share it in the comments section.