If you are targeting GATE this is a bad question - because only previous year GATE papers are enough to understand the questions coming and though they don't repeat the questions question types can be predicted.
If it is for exams like NET, ISRO etc. syllabus is a bit more than GATE and previous NET papers are good for it.
For high quality questions see previous TIFR papers. ISI and CMI papers are also excellent.
You can download the previous year question papers from http://previous.gatecse.in
PDF book for GATE Overflow can be taken from http://book.gateoverflow.in
