To configure syslog on ESXi to forward to a central logger, you can just use the VIC and go to Configuration->Advanced Setting->Syslog ->Remote.
To do this on a bunch of ESXi servers, you will want to do this programatically using either the vSphere vCLI (Perl) or PowerCLI (Power Shell). Get these tools free at http://www.vmware.com/go/sysadmintools.
In the vCLI :
vicfg-syslog.pl –p 514 –s < IP of your syslog server > –server < IP of your ESXi host>
Then enter root username, and root password of your ESXi host.
In Power Shell:
Set-VMHostSysLogServer -SysLogServerPort 514 –SysLogServer < IP of your syslog sever > -VMHost < IP of your ESXi host >
Update 6/23/2010 : See this website for caveat with syslog on ESXi http://www.virtuallyghetto.com/2010/06/esxi-syslog-caveat.html