Where can I find a vSphere Client for Linux / Mac OSX?

In vSphere 5 vCenter includes an optional web server component that is much better than earlier based on Adobe Flex that makes it possible to access the vCenter Server through a web browser in a quite similar fasion as the vSphere client. The vCenter Appliance comes preinstalled with the vSphere Web Client and can be used to give access to your virtual environment even if you're not running vCenter from the virtual appliance: http://longwhiteclouds.com/2011/11/05/deploy-vsphere-web-client-without-additional-windows-server-license/

VMware only provides a native Virtual Infrastructure Client (also known as VIC or viclient) for the Windows platform. VMware once said that a linux version of this client was in the works, but we suspect that the web client is where we're heading.

It is possible (with a few limitations) to run the native windows client under other OSes using WINE by following this howto: http://www.virtualinsanity.com/index.php/2009/02/02/vmware-infrastructure-client-on-ubuntu-an-update/

There used to be an open source client called Kodiak  (not full featured). It' was written in Adobe Flex and worked on many different client OSes. It seems however that this project is gone now.

If all you need is to access the consoles of the virtual machines it's also possible to use vmware-vmrc from the VMware Server 2.0 web interface (plugin that is installed through the web interface that can be used standalone) or to use iMKS - The Remote Console Appliance.

Another possibility is to use VMware Player as a remote console with the command: vmplayer -h ip.address.of.your.host