https://www.youtube.com/ - create a channel, add a video, write a 20-30-word description including your website's URL. Add 3-4 tags - your keywords. You can use your keyword in the video's title — it ranks very well.
You can do the same on https://vimeo.com/ and https://www.dailymotion.com/
https://www.facebook.com/ - create a business profile, add your website.
https://www.crunchbase.com/ - list your business, add your website, news.
https://www.linkedin.com/ - create a business profile with a backlink. Create some pages that describe your products/services.
https://www.slideshare.net/ - create a PDF document with a link to your website and upload it there.
https://soundcloud.com/ - upload a small audio presentation with a proper title and description. You can easily convert your text to speech online, just google for "text to speech mp3".
https://alternativeto.net/ - add your website, and your competitors to get listed among their profiles.
http://www.lacartes.com/ - list your business and website.
https://www.manta.com/ - add your business and website.
http://website.informer.com/ - type your website's domain, your listing will be created automatically.
https://www.cutestat.com/ - type your website's domain, your listing will be created automatically.
https://hypestat.com/ - type your website's domain, your listing will be created automatically.