There are some unconventional topics in both paper 1 and paper 2. There is no single source for these topics. This article covers PDFs for such topics. Most of the PDFs have highlighted texts to aid in revision at the last moment.
UPSC Sociology Paper 2 Click here
The above link has PDFs, links of websites of paper 2 topics difficult to find in standard books. These topics sound GS-like, however, we need to give a sociological touch to our answers.
Page no. of important books Click here
A particular topic mentioned in syllabus may be scattered across several pages in a book(s). The above link has a topic-wise compilation of important pages of books. It is currently a work in progress.
Challenges of social transformation (Paper 2) Click here
This is among the most dynamic portions of UPSC Sociology. The topics appear entirely GS-like. Also, UPSC has increased focus on these topics recently (~2015), since they are generally not covered by coaching institutes. The above link has PDFs of almost all subtopics, with highlighted text for easy revision.
UPSC Sociology Paper 1 Click here
PDFs of some unconventional topics in UPSC Sociology Paper 1.