Credit card issuers proved to us in 2011 that they are once again prepared to compete for the best customers by offering some amazing sign-up bonuses. Based on what we've seen so far this year, I think we can expect to see more of the same throughout 2012, but taking advantage of sign-up bonuses and earning rewards for the money you spend aren't the only ways you can profit from credit cards. Here are 5 ways credit cards can actually help keep more cash in your bank account this year: