You may refer to the Universal Device Poller which is installed as a part of NPM.
Start-->All Programs-->Solarwinds Orion-->Network Performance Monitor-->Universal Device Poller-->Add New Universal Device Poller-->Browse MIB tree
Once you reach to the MIB Tree,just start expanding and you will start seeing all available MIBs.
Alot of this depends on the type of device being polled. I have an internal list, if you DM me via thwack I will work with you offline to send you what you need.
You may find your answer in the following KB articles:
http://knowledgebase.solarwinds.com/kb/questions/1195/ (CPU and memory utilization)
http://knowledgebase.solarwinds.com/kb/questions/1199/ (generic, Cisco, and Aruba wireless)
The SolarWinds NPM Master MIB has literally tens of thousands of MIBs integrated. There is not likely a place that will list them all. Are you possibly looking for all the OID's that a MIB would have for a particular device maybe? If this is the case you can use the SNMPWalk tool in your Orion installation directory to connect to that device and get an exact list of all OID's available from that machine.