Paralleling Power Supplies
There are some switching power supply chips you can parallel because, provided one chip is master and the other is PWM slave, both sets of power transistors switch on and off together and there is no fight, just twice the amps. The TPS40180 is an example that specifically describes how to parallel up devices. TI seem to have a few like this although I've never noticed Linear Tech offering exactly the same functionality.

Linear power supplies chips like 7805 can be paralleled (without a scrap/fight) but usually one does all the work and overheats then goes and sulks while the other takes over - not an ideal result but no smoke is the main thing.