In marketing the avenues and channels are endless. In B2B the best approach is a highly targeted one. Discover where your target audience frequents, and meet them there. Shows, forums, events, etc.

I would also suggest investing resources in search marketing, SEM drives traffic and subsequent revenue. And well, if you don’t exist online nowadays, you simply don’t exist. As simple as that.

Lastly, in this Amazon era that we live in reviews are critical. We have become accustomed to checking the reviews of our peers before furthering any interactions with businesses and products. If you are a service, Clutch is extremely well reputable. For software, check into Capterra and G2Crowd.

For b2b, I got the perfect answer for you. You want to promote where entrepreneurs and other business minded people spend their time on the internet.

Upvotes Club's "Managed Marketing" service (https://upvotes.club/product-category/managed-services/) is what a lot of other marketing companies will resell you when you buy their marketing package and you say that your product/service is targeted towards other businesses.

From my own experience, for a machine learning - related Python library, they got me on the first page on lobste.rs, hacker news, reddit's /r/python, /r/machinelearning, etc. numerous times. Basically, they reached exactly my target market. It works for a good price, and I just gave you the direct source, no 3rd parties, to save you some money.

Good luck.

Could you give us a little more information? Are you looking for recommendations for marketing firms to help you promote your business? Or are you looking for the community to recommend businesses who could become customers?

Also, what is your B2B business?

These are in my bookmarks:
https://www.capterra.com/
https://www.g2crowd.com/
https://clutch.co/
http://www.saasgenius.com/
https://www.discovercloud.com/
https://trusted.de/
https://lespepitestech.com/
https://www.quelsoft.com/
https://kundennutzen.ch/
https://www.g2.com/
https://suitapp.de/
https://freesoft-100.com/
https://www.softwarefindr.com/
https://fitsmallbusiness.com/agorapulse-user-reviews-pricing/
https://reviews.financesonline.com/p/sprout-social/
https://www.marketingautomationinsider.com/
https://blog.hubspot.com/blog/tabid/6307/bid/10322/the-ultimate-list-50-local-business-directories.aspx

I would also suggest investing resources in search marketing, SEM drives traffic and subsequent revenue. You can also take suggestions from the web development company in USA.

Top B2B & Lead Generation Companies to Promote Your Business

1. CIENCE Technologies
2. ParamInfo
3. WebiMax
4. Vsynergize
5. Leadium
6. EBQuickstart
7. Callbox

Have you tried relevant LinkedIn Groups and partnering up with complementary B2B firms related to your business of course?