Just a few! ;-)
When the OVMWorld.org website was still vendor-independen, you would have found the Cadence-contributed OVM reference methodology kit on the user contributions page. Mentor now run the OVMWorld site and have blocked Cadence from accessing it, so I don't know if Cadence's contributions are still accessible there.
You can certainly find the UVM equivalent on UVMWorld.org (this site is owned by Accellera so should remain vendor-independent).
There is also a wealth of OVM / UVM material shipped with Incisive, as part of our SoC Verification Kit. The Kit is basically a full SoC design using lots of Cadence's own design IP, almost entirely open-source. We provide not just the example testbench code but also full self-paced workshop / training material for pretty much all verification flows (block-level OVM/UVM, block-to-system reuse, hw/sw co-verification, formal properties, lo-power etc etc). The best thing to do is crank up the help tool "cdnshelp" from your Linux/Solaris prompt.
In the hierarchy of help pages, look for "Incisive Verification Kits". Hopefully the image will attach here to give you a pointer to it.
We use these workshops to deliver training, so they're really comprehensive. Plus the Kit contains a lot of "free" VIPs to give you good examples to get you moving (of course our commercial VIPs are a league above this in terms of features, support etc, but that's another story ;-) )