Of course the RedGate books. If these guys are new to SQL Server and primarily in a support position, then I'd suggest they focus their learning track on backup / restore, security, and monitoring. They don't need to get side tracked by T-SQL programming or database design concepts, not until they are solid on the key areas for which they'll be receiving 2am support calls.
"Do not seek to follow in the footsteps of the wise. Instead, seek what they sought." - Matsuo Basho