I wasted several hours researching this a while back and came to the following conclusions:
Rzeppa joints (typically the large outer joints with six balls) are pretty forgiving as far as lubrication, but moly-fortified grease is recommended. Lots of options here, with most off-the-shelf options being a lithium based, moly-fortified grease (3% is common).
Tripod joints (typically the small inner joints with three needle bearing rollers) are not served well by the same moly-fortified grease. They typically want a lighter weight polyurea grease which can be hard to find. Aside from biting the bullet and buying the little pre-packaged grease specific to your manufacturer (i.e., Honda, Subaru, etc. typically offer two separate tubes for the different style joints used), the only readily available and inexpensive option I found was John Deere's multipurpose polyurea grease. It's thicker than what the manufacturers sell in the little tubes, but it's closer in composition than anything else I found.
For my son's Subaru, we recently used John Deere's moly-fortified lithium grease on the Rzeppa joints and their polyurea multipurpose grease on the inner tripod joints. Lots cheaper than buying the specially packaged tubes from Subaru.
AM.