I want bookmarks specific to aiding in programming tasks, not to every task.
If the bookmark is awesome to every user, please don't post it as an answer here. I will down vote it and I suggest to users do the same. To general bookmarks, please post on Webapps.StackExchange
Good answer is a bookmark which helps the programmer work.
I don't expect get too many answers although it would be a great surprise if it happens.
Please, explain what the bookmark does and where it can be used.