Great Commanders have the ability to recruit. The civilopedia entry says nothing, so I was hoping to get a clarification on how many units are recruited, what type of units are recruited, and what effect, if any, it has on the city the Great Commander is in.

I dunno but I tried it once and got a couple of crappy units. Not worth a great leader IMO.

Its good for two things:
1. Defending a city.
2. Using in a just captured city to keep up the momentum of your offensive.

The thing that needs to be done to make the units useful is to make it so that they get XP as though they were built in the city.

The machanic is that it randomly picks a few t3 units and tries to get as close to making them as possible given the techs you know. So if it goes to make an assassin and you dont have poisons it will try to make a hunter, if you dont have hunting then you will get a scout.

The amount of recruits that you get is 1/3 the population fo the city +1. This number is doubled if there is a Enforcement Office in the city.