Red Gate (homepage)
System for continually auditing all servers and workstations in the domain, including physical details and specs, plus software installed on them.
Nice little free tool for determining where all the space is being used up on a machine
SSMS Tools Pack (homepage)
A collection of very useful addin features for SQL Management Studio, such as code snippets, connection colour coding, SQL formatting - and last time I looked, it was still free as well.