Copy, rename, and delete files between folders and computers.
If you're looking for a convenient, uncomplicated, and stable synchronization tool, you could do much, much worse than Microsoft's SyncToy. Part of the Windows XP PowerToys add-ons, this tool makes it easy to keep folder contents identical on one machine or across a network.
Convert MSG files to multiple formats like PST, PDF, EML, EMLX, DOC, Office 365, and Zimbra.
Nice and easy to use tool to calculate IPv4 networks an IP addresses.
Update: NetDiag, net diagnostic tool