The vCLI is the vSphere command line interface which was rebranded from the RCLI with the release of vSphere. The vCLI are a set of Perl scripts that provides a similar interface to some of the well known esxcfg-* commands that are found within the classic ESX with the Service Console. These scripts utilize's the vSphere API and specifically the vSphere SDK for Perl bindings to allows administrators to remotely manage and configure both ESX and ESXi. vCLI is officially supported on Windows and Linux OSes, but some users have gotten it to work on Solaris and MAC OSX. 

Here are some new/updated utilities included with the release of the vCLI 4.0

System Management

vicfg-advcfg / esxcfg-advcfg

vicfg-module / esxcfg-module

vihostupdate [for ESX(i) 4.x+]
vihostupdate35 [for ESX(i) 3.5]

This was never implemented in VIMA 1.0 and looks like it's been removed in vMA 4.0

Network Management

vicfg-route / esxcfg-route

vicfg-vmknic / esxcfg-vmknic

vicfg-vswitch / esxcfg-vswitch

Storage Management

esxcli (Take a look at Duncan Epping's post for more information)

vicfg-iscsi / esxcfg-iscsi

vicfg-mpath / esxcfg-mpath

vicfg-nas / esxcfg-nas

vicfg-vmhbadevs / esxcfg-vmhbadevs

vicfg-volume / esxcfg-volume (Take a look at Duncan Epping's post for more information