Build a distributed system that searches twitter feeds in real time and allows anyone to perform searches from a web front end.
Build a distributed file system. Implement distributed B*Trees or B+Trees as the base of this file system. Do it in erlang.
Build a distributed key value store on top of the distributed file system built in step 2.
Build a distributed web index (to be used by a distributed web search engine) on top of the key value store.
Build a distributed linker. Advanced build automation offers remote agent processing for distributed builds and/or distributed processing.
Build a MMORPG backend that relies on distributed storage of the game/player state and distributed processing of user requests.