Update: Links that changed were corrected
First, use this Rails guide to configure ODBC, FreeTDS, RubyODBC:
http://wiki.rubyonrails.org/rails/pages/HowtoConnectToMicrosoftSQLServerFromRailsOnLinux
I also installed the ActiveRecord ODBC Adapter and DBD-ODBC from source
Check this for a hack when DBI can’ find the driver: