VMware has released their hardening guide for vSphere 4.0.
There is more than 100 guidelines to choose from, divided between
http://blogs.vmware.com/security/2010/04/vsphere-40-hardening-guide-released.html
Time keeping in a virtual environment can be a challenge to setup.
To help you, VMware has maintained a KB on the subject.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1318
The KB presents best practices for achieving accurate timekeeping in Windows Guest operating systems. These recommendations include a suggested configuration for timesynchronization in the guest and on the host.
A more specific guide also exists for Windows and Linux servers:
For Windows read:
http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=1318&sliceId=1&docTypeID=DT_KB_1_1&dialogID=73678717&stateId=0%200%2078515868
For Linux read:
http://kb.vmware.com/selfservice/microsites/microsite.do?cmd=displayKCPopup&docType=kc&externalId=1006427&sliceId=1&docTypeID=DT_KB_1_1
It’s great reading, but very nerdy 
vLogView, helps you view and search all LOG files from each of your ESX hosts from a single application.
For more info and the latest download, visit http://xtravirt.com/xd10132
If you need a good guide to Interpreting the statistic from ESXTOP then take a look at this guide from VMware.
http://communities.vmware.com/docs/DOC-9279
I’m using it to troubleshoot performance issues (poor response times) from clients in different locations, when using the remote console.
If you are looking for a easy and simple guide for setting up iSCSI on vSphere (ESX 4.x) you might want to take a look at this guide from www.techhead.co.uk
http://www.techhead.co.uk/vmware-esxi-4-0-vsphere-connecting-to-an-iscsi-storage-target
Many admins have upgraded to Windows 7 and gotten into problems when trying to install the vSphere Client.
I have found a few guides to do a workaround, but the best guide is found at techhead.co.uk.
http://www.techhead.co.uk/running-vmware-vsphere-client-on-windows-7
Thanks to Kiwi Si.
Last week I upgraded a Virtual Center server from Win2003 & MSSQL 2000 (32-bit) to Win2008 & MSSQL 2005 (64-bit).
During the installation of vCenter it asked for a 32-bit ODBC even though all the new systems was running 64-bit.
After a some time on Google i found that Windows 64-bit also includes a 32-bit version of the ODBC.
To set up a 32-bit DSN launch the 32-bit version of the Data Source Administrator. It is located at:
%systemdrive%\Windows\SysWoW64\Odbcad32.exe
Also se
http://www.vmwarewolf.com/32-bit-odbc-dsn-for-vsphere/
Duncan Epping has released a great post on how to partition your ESX 4.0 (vSphere) using scripting and the grafical installer
http://www.yellow-bricks.com/2009/05/27/partitioning-your-esx-host-part-ii/
You cannot define the sizes of the /boot, vmkcore, and /vmfs partitions when you use the graphical or text installation modes. You can define these partition sizes when you do a scripted installation.
The ESX boot disk requires 1.25GB of free space and includes the /boot and vmkcore partitions. The /boot partition alone requires 1100MB.
The vmcore is created automatically by the installer
Primary:
/ - 5120MB
Swap - 1600MB
Extended Partition:
/var - 4096MB
/home - 2048MB
/opt - 2048MB
/tmp - 2048MB
VMware have released a demo on YouTube that shows a “must have” for PowerShell users who automate and manage vSphere and vCenter through PowerShell.
The project is named “Onyx” and works like a middelware between the vCenter Client and the vCenter Server.
Onyx is unfortunately still in a private beta and therefore not acceble to the Public…….. 
Read more on rtfm-ed.co.uk.
http://www.rtfm-ed.co.uk/?p=1643
Or read more on the “get-scripting podcast” blog
http://get-scripting.blogspot.com/2009/08/get-scripting-podcast-episode-12-carter.html
http://communities.vmware.com/message/1286580#1286580
http://www.ivobeerens.nl/?p=256
http://www.configuresoft.com/esx-compliance-checker.aspx
http://www.vmware.com/support/developer/vima/
http://www.run-virtual.com/?p=233 (VMware CPU Host Info)
http://teckinfo.blogspot.com/2009/01/vdiagram-document-your-vi-with-one.html (vDiagram)
If you want to perform an offline upgrade of an ESX 3.x host to the new vSphere host there are a few ways.
Using a DVD:
/root/esxupgrade.sh storage1
Using the DVD ISO:
esxupgrade.sh -i /vmfs/volumes/storage1/esx4.iso /vmfs/volumes/storage1
storage1 – should be a VMDK local datastore attached to the host.
storage1 – should be at least 8.4GB in size.
Techtarget.com has released their Top 10 pick from VMware to tryout in 2009.
Read it.
