12 Alternatives to LinkedIn

1. Makerbase - for individuals who make software, such as apps and websites launched in 2015 by ThinkUp’s founders – Lifehacker founding editor Gina Trapani and entrepreneur Anil Dash.
2. LunchMeet - iOS app influenced by the book “Never Eat Alone: And Other Secrets to Success, One Relationship at a Time” by Keith Ferrazzi and Tahl Raz and uses LinkedIn’s API so that you can schedule impromptu lunch meetings with your LinkedIn contacts in order to create meaningful face-to relationships.
3. Xing - founded in 2003 where you can find jobs, partners, advice, or list an opening in your business and the largest business network in German-speaking countries and has more than 14 million members. 
4. Plaxo - launched in 2002 by Napster co-founder Sean Parker, Plaxo is an online address book that automatically update, synchronize, recover, and unify your contacts. 
5. Beyond.com - proudly calls itself “The Career Network,” and since 1998 it has connected more than 45 million professionals with a wide-range of companies involved in the technology, healthcare, business, and marketing industries. 
6. Data.com Connect - Salesforce’s Data.com Connect provides both the phone number and email address of companies listed in its business directory. 
7. Sumry - publicly launched in 2014 and is a web app that builds online resumes and portfolios uniquely highlighting your education, certifications, skills, work experience, and even testimonials from people you have worked with in the past in a full timeline, as opposed to just another resume.
8. Jobcase - has been powering more than 100 job sites since 2009 but only entered the social media networking scene until 2015 as a way to ask questions or join groups relevant to your industry allowing you to create a comprehensive profile that describes not only your education and experience, but also your preferred salary, work conditions, personal traits, and whether or not you’d be willing to relocate. 
9. EFactor - founded in 2008 becoming the world’s largest entrepreneurial community where members have access to both online and offline access to the people, tools, and resources to make meaningful connections.
10. Bark.com - launched in 2014 and helps matches member to local businesses. 
11. Doostang - founded by Stanford University in 2005 as an online career networking community that help members locate career opportunities in finance, consulting, technology, media, and entertainment. 
12. LocalsNetworking - since 2013, it has been providing a platform for members to build their own referral network in their community.

Sources:

https://www.searchenginejournal.com/12-professional-networking-alternatives-linkedin/139681/