More information here: http://heartbleed.com
This site will check a URL for the vulnerability: http://filippo.io/Heartbleed/
This command line tool also checks for the vulnerability- its a python script you can use inside your firewalled zones.
Our ESXi 5.5 build 1331820 servers have the vulnerability.
And fully patched ESXi 5.5 build 1623387 (as of 4/8) shows the vulnerability as well.
I've posted in the vmware forums asking about the ETA of a patch to fix this in our VI.
Update 4/9: VMWare has supplied a KB of products affected
Update 4/19 - Patch Released:
Note: VMWare recommends updating vCenter before ESXi
VMware KB: Resolving OpenSSL Heartbleed for ESXi 5.5 - CVE-2014-0160
Confirmed the vulnerability is removed by this patch - folks should also cycle keys and update passwords
chmod +t rui.crt
chmod +t rui.key