Hootsuite provides a great way of comprehensively managing all social media platforms. But, it is paid and you can only use the free trial version for 30 days.
Here some of the free alternatives:
TweetDeck (By Twitter)
TweetDeck is a free Twitter management app. Using this platform, you can schedule Tweets, segregate your flow in several feeds, and create feeds for notifications and DMs.
Blog2Social works in a similar way to RSS-to-social posting. You can use this platform to automatically cross-post across various social channels such as Facebook, Google Plus, Twitter, Instagram, LinkedIn, etc.
Content Studio is a great tool for startups and small businesses. In the free version of this platform, you can use two social media accounts and schedule up to 500 posts in a month.
As the name suggests, this platform proofs your content before you post it. You can schedule posts, maintain an editorial calendar, and create reusable posts.
Later was originally launched specifically for Instagram. Using this tool, you can post on Instagram without much hassle. These days, this tool also offers the scheduling of Facebook, Twitter, and Pinterest.
Few other mentions include: