Powershell remoting with V1
I think PrimalScript's Remote Script Execution Engine would do what you're after. It does require a small service to be installed on remote computers, but you get unlimited licenses for that when you buy PrimalScript (Enterprise edition).
There's also a PSHRemoting project someone did.
N Software's NetCmdlets also come with a "PowerShell Server" (http://nsoftware.com/powershell/) which enables remoting.
There is a great article up on the PowerShell team blog that describes how to get some basic remoting working in V1.
Basically, PS V2 uses Windows Remote Management (WinRM) under the hood. Winrs is the command line tool used to work remotely with machines.
This tactic that Jeffrey talks about uses WinRS and some PowerShell trickery to get remoting working in V1. Its not as slick as V2, but you can definitely get some basic stuff working with it.
I have used PSExec successfully. You can also use WMI to kick off remote processes. Here is an example.