This is my third post in this challenge. My previous entry to this challenge:
What’s The Best Thing That Happened To You Because Of Steemit? - May 30 Days Writing Challenge by @dragosroua.

Let's start by saying that I did not spent much time about learning what a witnesss is on Steemit, so I have read the FAQ (What are Steem witnesses) during the writing of this post.

Voting for up to 30 witnesses? Mentioning the 5 most relevant witnesses?

I don't think that I will ever vote for 30 witnesses. In fact, but I can mention 5 of them.

Apart from this and based on the mentioned witnessess, I can say the following:

@utopian-io
This is currently maybe one of the best projects on the Steem blockchain.
Utopian rewards open source contributors, such as translations, developments, graphics designs, tutorials, video tutorials, bug reports, suggestions, analysis, blog posts, documentations.
The rules are very strict and the quality of the approved contributions are excellent.

@jesta
As @dragosroua said, "He is behind some of the most interesting spin-offs on top of the Steemit blockchain, and yet, very few people know about him."
I know him as the creator/owner/author of the ChainBB forum. This was an experimental forum on top of the Steem blockchain. Yes, it was. Because he is shutting down ChainBB.
I used it rarely. There was a lot of spam post/comment, but the basic conception of the forum was very good. The Steem blockchain should have a forum like the ChainBB.

@arcange
For designing the @steemitboard. The Steemit Board of Honor. This project helps everyone on Steemit. This project gave me a lot of inspiration after I registered on Steemit. This project keeps track of your statistics on Steemit and upvote your post and tell you, if/when you reach some kind of milestone/achievement. These milestones/achievements are dynamic/continuous, so you can reach them multiple times.
The @steemitboard project currently only have 1624.996 Steem Power and nowadays the account upvotes the posts of the community with 1% voting strenght. I think that this project deserves much more Steem Power. I really hope that they will get more Steem Power in the future, because they are really inspiring/supporting the Steemit community.
For more information, please visit their website: https://steemitboard.com.
As their website says: "SteemitBoard is the place where you can receive rewards for your achievements on Steemit."

@aggroed and @ausbitbank
For creating the @minnowsupport. The Minnow Support Project. With all the helps, tips and suggestions for the minnows and beginners, and the community building opportunity (including post promotion and free upvotes from bots), I think that they deserve a place in the top 5 most relevant witnesses on Steemit.
For more information, please visit their website: https://minnowsupportproject.org.

This is all I can currently mention/say about the witnesses.

Thank you for taking the time to read my post and thank you to all of you for your continuous support!

See you tomorrow!