Angry IP Scanner

For network scanning, Angry IP Scanner is a sweet little program that does the trick. Cross-platform, has nice internal options, and if you know Java, you can write your own plugins.

Ammyy.com Remote Admin Tool

For remote admin with users who have a working internet/LAN connection, this is the bomb.

Spiceworks Network Manager

Spiceworks Network Manager seems too good to be true, a free network management utility. But, it does seem to be what it says it is. Easy-peasy, not even queasy to install. And it does what it says it does, inventory, monitor and report. Did a bit of Googling on it to see if there were any gotchas, none thus far.