Anything higher-level, and more comprehensive than pipes/sockets?
Yes, there are lots of things, but there isn't one as "Standard" as COM/DCOM. At least, in Windows, COM / DCOM are used by "Windowsish" stuff, and other RPC mechanisms are used by un-"Windowsish" stuff.
Linux doesn't have anything like that, instead things which need higher level RPC protocols typically use whatever their language provides, or a specific library which best suits an app's needs. Examples of that would be RMI in Java, Python's "pyro" module, etc, which will provide (some) functional parity with DCOM.
Corba is a bit heavyweight but some people apparently do use it.
A lot of applications roll their own RPC libraries. Don't do that unless you have to, it's nasty.