Where to search for conferences and workshops in computer science?

A very good site for CS conferences and journals call for papers and their respective deadlines is A Wiki Calls for Papers.

There are lots of different websites and mailing lists for different subjects. Some researchers also maintain webpages of conferences in their area. I mostly learn about conferences through two mailing lists I subscribe to and two researchers' webpages, as well as emails forwarded by my mentor (I'm a postdoc).

Probably the best thing would be to ask your supervisor how he finds conferences. He'll probably know the best sources for your research area.

One fairly general website I know about is www.conference-service.com, but in my area it's far from complete.

If you are serious about publishing, try one of these conferences. These conferences are good, even at Rank 3. You also have the list divided by the area of interest.