For the uninitiated, there are two basic kinds of scripting arenas available for VMware admins: the vSphere CLI, based on the traditional Windows batch file implementation, and vSphere PowerCLI, based on PowerShell. Both have lots of functions.
The following example is my vCLI-SetRoundRobin script (downloads as a ZIP file). I have shrunk the font for format on the page. This script will go through and not only set defaults for all the various Storage Array Type Plugins (SATPs) to the Path Selection Policy (PSP) Round Robin, but will also reassign existing LUNs by rerunning the ESX storage claimrule load function (ESXi 4.1). Otherwise you can reboot your host afterward.
Here is my vHostListIPs script that will go out and query the currently connected VI-Host (vCenter or single ESXi host) and list the IPs on the first vNIC of the VMX configuration file. Useful for updating Excel worksheets and such, and checking for misconfigurations when doing large deployments.
A great resource is the vSphere PowerCLI Sample Scripts Library; it contains a lot of items that you can use to get started right away.