Looking at it from a Unix-a-like background Powershell provides a script capable shell (ala bash and friends) including built-ins that do useful stuff in some of the posix and gnu externals commonly called from shell scripts. Rather than working primarily on text and streams like most unix-a-like shells it is object based. Through the relevant modules and the objects they provide it allows pretty complete interaction with the Windows management infrastructure so in the right hands it can be very powerful. See http://en.wikipedia.org/wiki/Windows_PowerShell. On any Windows machine that isn't obsolete or close to (the 2003 editions fall out of support very soon and XP already has, anything newer had PS integrated) you'll find at least v2, usually v3 or higher.

I keep meaning to find a good book or online reference and spend some time properly learning how to use the thing... For some things it'll replace my need to have cygwin installed everywhere, and it might allow me to do some stuff "better".