Many printed reference dictionaries and encyclopedias of sociology (and the social sciences in general) can be found in the Arts and Social Sciences Library. They can be used to get a good overview of the subject, or to research specific aspects of it.
Some of the best ones are:
The Penguin dictionary of sociology (HM 17 ABE)
The Sage dictionary of sociology (HM 17 BRU)
Blackwell encyclopedia of sociology (HM 425 BLA)
The Cambridge dictionary of sociology (HM 17 CAM)
The concise Oxford dictionary of sociology (HM 17 CON)
The international encyclopedia of the social sciences (Oversize H 40.A2 INT) (also available electronically)