Spatial and Temporal Inference Rules
Regarding spatial reasoning, I think the best way to start with this would be to work in a Minecraft context ... a couple GSoC students in summer 2015 finished the "plumbing" to make OpenCog interact with Minecraft agents, but didn't actually make Minecraft agents that do anything...
A start would be to write some scripts in OpenCog similar to these (which are for controlling a robot head)
https://github.com/opencog/opencog/opencog/eva/behavior.scm
but for controlling a Minecraft agent...
Then, in the context of that agent, one could have the agent do some spatial and temporal reasoning in Minecraft
Some temporal reasoning rules were coded in the old python version of PLN
https://groups.google.com/forum/#!topic/opencog/HGCRIHBlnpg
and need to be ported to the new, Unified Rule Engine version of PLN .. this is also a good "advanced beginner" task ... The truth value formulas in these rules might be improved by attention to the ideas in this paper
https://users.cs.cf.ac.uk/S.Schockaert/Publications_files/fuzzyAllenFinal.pdf
(An alternative approach to the truth value formulas was prototyped in
https://github.com/keyvan-m-sadeghi/interval-algebra-paper/blob/master/IntervalAlgebra.pdf
but there are still some unresolved issues with that approach.)
Regarding spatial reasoning, following the pattern of the temporal reasoning mentioned above, one would like to have a RCC-3D version of
https://users.cs.cf.ac.uk/S.Schockaert/Publications_files/fuzzyRCCreasoning.pdf
integrated with PLN...
The Minecraft world would be a good venue for experimenting with this stuff...