Here are some thoughts and inspiration on PiHole blocking lists.

Useful 👍

FilterHeroes - KAD

based on KAD (Github | Website) which is a filter list for AdGuard and uBlock Origin
new hosts can be proposed by a form on the KAD website or as an Issue in the GitHub repository
GitHub repository

https://raw.githubusercontent.com/FiltersHeroes/KADhosts/master/KADhosts.txt

Firebog

WaLLy3K maintains a well curated list of lists on firebog.net. He classifies them in different categories based on their probability to contain false positives.

https://v.firebog.net/hosts/static/w3kbl.txt	
https://v.firebog.net/hosts/AdguardDNS.txt	
https://v.firebog.net/hosts/Admiral.txt	
https://v.firebog.net/hosts/Easylist.txt	
https://v.firebog.net/hosts/Prigent-Ads.txt	
https://v.firebog.net/hosts/Prigent-Crypto.txt

FadeMind

A collection of hosts files made for the Steven Black hosts project.

https://raw.githubusercontent.com/FadeMind/hosts.extras/master/add.Spam/hosts	
https://raw.githubusercontent.com/FadeMind/hosts.extras/master/UncheckyAds/hosts	
https://raw.githubusercontent.com/FadeMind/hosts.extras/master/add.2o7Net/hosts	
https://raw.githubusercontent.com/FadeMind/hosts.extras/master/add.Risk/hosts

AdroitAdorKhan - antipopads:re

GitHub repository
block pesky malicious pop ads

https://raw.githubusercontent.com/AdroitAdorKhan/antipopads-re/master/formats/hosts.txt

Adaway

AdAway is an open source ad blocker for Android using the hosts file
Special hosts file for AdAway containing mobile ad provider

https://adaway.org/hosts.txt

AnudeepND

GitHub repository
advertisements, malwares, spams, spyware & trackers
Each domain is tested and verified before addding to the list
New hosts can be submitted via GitHub issues

https://raw.githubusercontent.com/anudeepND/blacklist/master/adservers.txt

Crazy-max

Website
Github repository
block spying and tracking on Windows systems

https://raw.githubusercontent.com/crazy-max/WindowsSpyBlocker/master/data/hosts/spy.txt

DandelionSprout

Created by Imre Kristoffer Eilertsen
GitHub repository

https://raw.githubusercontent.com/DandelionSprout/adfilt/master/Alternate%20versions%20Anti-Malware%20List/AntiMalwareHosts.txt

Disconnect.me

Website
List of tracker hosts

https://s3.amazonaws.com/lists.disconnect.me/simple_ad.txt	
https://s3.amazonaws.com/lists.disconnect.me/simple_malvertising.txt

Frogeye.fr

Website
Created by Geoffrey Preud'homme
List of tracker hosts
Multiple flavours available

https://hostfiles.frogeye.fr/firstparty-trackers-hosts.txt

Digitalside.it

Website
Created by Davide Baglieri
Based on a database of malware samples

https://osint.digitalside.it/Threat-Intel/lists/latestdomains.txt

Phishing.army

Website
Created by Andrea Draghetti
Generated every 6 hours from PhishTank, OpenPhish,
Cert.pl, PhishFindR Urlscan.io and Phishunt.io reports.
Each domain is analyzed to eliminate false positives,
through the Whitelist of Anudeep and the Alexa Rank

https://phishing.army/download/phishing_army_blocklist_extended.txt

Spam404

GitHub repository
Submissions via this form
Updates are rather rare

https://raw.githubusercontent.com/Spam404/lists/master/main-blacklist.txt

Abuse.ch URLhaus

Urlhaus as a subproject of abuse.ch to share malware distribution sites with the community, AV vendors and threat intelligence providers
Accepts non-anonymous submissions via form or API → see here
Statistics

https://urlhaus.abuse.ch/downloads/hostfile/

Zerodot1

Gitlab repository
helps preventing cryptomining in the browser or other applications

https://zerodot1.gitlab.io/CoinBlockerLists/hosts_browser

Monstanner

GitHub repository
contains fakeshops / affiliate stores on the German version of DuckDuckGo

https://raw.githubusercontent.com/Monstanner/DuckDuckGo-Fakeshops-Blocklist/main/Blockliste

AssoEchap

GitHub repository
List of stalkerware hosts: Indicators of compromise (IOC) for Stalkerware and Watchware applications for Android and iOS
Created by https://echap.eu.org/ (Association de lutte contre les cyberviolences sexistes)

https://raw.githubusercontent.com/AssoEchap/stalkerware-indicators/master/generated/hosts

RPiList

GitHub repository
Takes hosts data from other sources that can not be used with the PiHole in their original format and translates them to PiHole compatible hosts files (see here for more information)
Created by SemperVideo
Overview of all flavours

https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/notserious	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/crypto	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/gambling	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/Fake-Science	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/DomainSquatting1	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/DomainSquatting2	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/DomainSquatting3	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/DomainSquatting4
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/easylist
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/spam.mails

Blocklistproject

GitHub repository
Manually maintained
Many different categories → see here

https://blocklistproject.github.io/Lists/abuse.txt	
https://blocklistproject.github.io/Lists/ads.txt	
https://blocklistproject.github.io/Lists/crypto.txt	
https://blocklistproject.github.io/Lists/fraud.txt
https://blocklistproject.github.io/Lists/gambling.txt
https://blocklistproject.github.io/Lists/malware.txt	
https://blocklistproject.github.io/Lists/phishing.txt
https://blocklistproject.github.io/Lists/ransomware.txt
https://blocklistproject.github.io/Lists/scam.txt
https://blocklistproject.github.io/Lists/tracking.txt

winhelp2002

Another hosts list, also recommended by Adaway

Website

https://winhelp2002.mvps.org/hosts.txt

Yoyo

Another hosts list, also recommended by Adaway

Website
Used to have a form for submitting ad servers, but it is disabled until further notice, because there was to much spam
Can be customized using query strings → see here for more information

https://pgl.yoyo.org/adservers/serverlist.php?hostformat=hosts&showintro=0&mimetype=plaintext

Too agressive 👎

https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/Phishing-Angriffe	
https://raw.githubusercontent.com/RPiList/specials/master/Blocklisten/malware	
https://v.firebog.net/hosts/RPiList-Malware.txt	
https://v.firebog.net/hosts/RPiList-Phishing.txt

Where to find new filter lists

If these filters are not enough for you, you might find some other great lists at filterlists.com (a fantastic project made by Collin M. Barret).

Check if ad-blocking works

There are some tools to test if your adblocker is working:

Blog posts