Rick Scherer posted a blogpost about some reference cards for VMware admins:
First is the vmreference VI3 card by Forbes Guthrie over at www.vmreference.com
Second and third are VI3 Command References and Linux Command References from the VMware Deploy, Secure & Analyze class.
Source: http://vmwaretips.com/wp/2008/12/12/esx-reference-cards/