I am living in an area where line voltage is 220V. If I have access to all 3 phases, is it possible to create a "socket" with output voltage of ~110V, without use of a transformer? This is primarily a thought experiment, rather than a project with definite scope.
Triac based light dimmers do this.
Varying the firing angle of the gate results in a reduced RMS output voltage. The output from this can be rectified and filtered however extreme caution should be exercised because the circuit has no galvanic isolation from the Neutral/Active lines and cannot be earth referenced if ELCB's are intalled.
Have you checked all legs against neutral? Some 3 phase transformers tap so that two legs are 110v. http://en.wikipedia.org/wiki/High-leg_delta