program persistence layer in MathDataHub
In the OpenDreamKit project our colleagues developed the pypersist package that allows programmers to (easily) make their results persistent. We should have a more semantic version of this as part of MathDataHub, so we can get at interesting data and index them.
An example is a polynomial factorization service (with caching) This is a service that just caches factorizations and looks them up. Details at https://github.com/KWARC/mws/issues/102 I really think that (if done right) this would have quite an impact.
But the general project is much greater.