The minnow support team had an upvote service on Discord. You had to wait 30 hours before sending a post in. They later upgraded to a site called Palnet.io which is like Steemit. You can trade your credits on Palnet for an upvote. I like this system better because you can send a post in through Palnet anytime you want and you get a higher upvote depending on how many credits you sent in.
This replaces the Steem vote credits.io site that closed due to the owner not being able to keep it running.
This is a good system for bloggers like me who put so much time into their content but the content goes unnoticed.