It just depends on the type of problem you'd like to solve. I've got a whole bunch of ETL helper functions and patterns i've written for my business that could

It just depends on the type of problem you'd like to solve. I've got a whole bunch of ETL helper functions and patterns i've written for my business that could be packaged up as an extension if I were so inclined for example. Those are all SQL or PL/PGSQL functions, so no need for native code there though... For PostGIS, a whole lot of that code is just SQL or PL/PGSQL functions...but there are quite a few C functions as well, to take care of the heavy lifting which is less efficient to implement in SQL or PL/PGSQL.