Is there a command to specify which type of Villager to spawn?

Villagers use the Profession and Career tags to determine their type, as detailed on this wiki page. Profession ranges from 0 (Farmer) to 4 (Butcher) and determines the skin of the villager. Trades and actual job are determined by Career, the range and meaning depend on the profession.

/summon Villager ~ ~ ~ {Profession:0, Career:1}
/summon Villager ~ ~ ~ {Profession:2, Career:1}

Can be used to create a Farmer and a Cleric villager, respectively.

(Note: I didn't test it myself (not at comp), so there might be errors in the command structure.)

/summon villager ~ ~1 ~ {Profession:0,Career:0}

The "~ ~ ~" are the coordinates (location) where the mob will spawn, the first and third are lateral directions, and the second means the height. In my command there, it means the villager will spawn 1 block above wherever you run the command.

The profession is the type of villager you want.

• 0 = Farmer, Fisherman, Shepherd, Fletcher
• 1 = Librarian
• 2 = Cleric
• 3 = Armorer, Weapon Smith, Tool Smith
• 4 = Butcher, Leatherworker

You can even change their name.

/summon Villager ~ ~1 ~ {CustomName:0}

Where the "0" is is where you can put in your own name to give them.