1.GATE question @GATEOverflow
2. TIFR Questions
3. Reference book questions (Too many to mention) Keneth Rose Discrete, Automata Peter Linz, Algo Cormen & So on. You can find list on book.
Right now GATE + TIFR is more than enough ! If you have time do Reference book questions..
Give test series for Timing practice..That too Full Lenght. Other tests are useless most of time !