There seem to be a bunch of questions posted that have pretty good answers, but the asker hasn't yet accepted any. What is the best way to bump the asker to accept one?
Vote up the answers you think are good. The community consensus is just as important as the checkmark for the OP's "acceptance". Indeed, "accepting" an answer is entirely optional - a question is considered "answered" (for the purpose of statistics and the unanswered page) if it has an answer with a positive score.
Also, if the asker comes back and sees an answer with a lot of votes, they might be more inclined to accept that answer.