I try to ignore for as long as possible.  I find it really picks up after attending a conference like national or state SHRM.  With the size of our organization, I'm not in a position to make any decisions about the things they're trying to sell us on, and am not about to throw the leaders that do make those decisions to these wolves!  If we're looking for a new service, we know where to find them!

My go to for email is "Thank you for your message. We are not adding any tools to our toolbox at this time. If things change, I'll be in contact." Sometimes it gets them to back off and sometimes they just keep sending messages. After that, I ignore them.

I just counted.  So far today I've received 62 emails.  25 of those were from people trying to sell something.  Hopefully, most of these folks understand that they will be ignored and don't take that personally.  I only respond if they hit me with something that I happen to be interested in because of a project I'm working on.

I completely understand this, but as a small business owner providing HR consulting services, this is hard to hear. I was on the other end, politely waving off vendors, and I know how frustrating that can be. I never want to be in the business of selling someone something they don't want or don't need. Instead, I'm working to build meaningful relationships and networks and having faith that focusing on relationships first will eventually bring business. Frankly, I don't have the energy to conduct my business any other way. We are all people, and unless we focus on people first, the rest will be exhausting and fruitless (even if profitable). 
I know there are folks out there that need what I'm offering, but I'm struggling with getting my foot in the door (because my services are such a niche). Can anyone give advice how to promote mutually advantageous relationships between HR professionals and firms like mine? Or, if you want to connect, that would be cool too! I promise, NO SALES CALLS.