Idera's SQL Check has been updated to support SQL Server 2005. SQL Check is a free performance monitoring tool, not anywhere near as powerful as Idera's SQL Diagnostics Manager. However, it is free, which may be of some benefit to smaller companies, especially non-profits.
You can download the new version here: http://www.idera.com/Products/SQLcheck/Registration.aspx (as you might guess, registration is required).
IT Security, MySQL, Perl, SQL Server, and Windows technologies.