Seed nodes are crucial for the reliability of the Steem blockchain.
There is no economic incentive to run a seed node. It costs money to run the server, and it doesn't earn the operator any money for doing it.
For this reason, the witnesses (who are paid by the blockchain for their services as a witness) are expected to run seed nodes if they are financially able to do so.
Some non-witnesses (such as developers) may also chose to run public or private seed nodes to help provide reliability to other nodes that they are operating.
Every node operator is responsible for configuring a list of seed nodes in their node's configuration file.
Some node operators will connect to private seed nodes (ones that only they control and can access) but the majority of node operators will use publicly available seed nodes.
Having reliable seed nodes with low latency near your node helps your node to stay up to date with the latest blockchain data at a pace that is fast enough to keep up with the three second block times.
When node operators are configuring their seed nodes, it is recommended to ping all of the available seed nodes to determine the latency times from your node. (Which nodes will have low vs. high latency for your specific node will vary based on the location of your node compared to the seed nodes.)
Once you know the latency from your node to all of the available seed nodes, it is recommended to configure the seed nodes with the lowest latency near the top of the config file.
There are currently two places that a list of public seed nodes is available:
@wackou :https://status.steemnodes.com/Sometimes witnesses submit pull requests to add their nodes to the list(s), but the maintenance of is primarily done by 
seed-nodes channel of steem.chat.
Over the years, the lists have become outdated in various ways:
seed-nodes channel or submitted a PR to add them to both lists.I am planning to submit pull requests to both repositories to update the lists:
Here is a summary of the changes I plan to make:
steemseed-fin.privex.io:2001 
seed.jamzed.pl:2001 
seed.steem.prcolaco.com:2001 
seed1.cryptobot.news:2001 
seed.thecryptodrive.com:2001 
seed-east.steemit.com:2001 
seed-central.steemit.com:2001
seed-west.steemit.com:2001
seed.xeldal.com:12150 
seed.brandonfrye.us:2001 
seed.firepower.ltd:2001 
94.23.33.61:2001 to seed.timcliff.com:2001 
seed.blackrift.net:2001 to seed.steemian.info:2001 
node.mahdiyari.info:2001 
192.99.4.226:2001 
@dele-puppy134.255.253.142:2001 
@maxlxl104.236.82.250:2001 
@svksteem.kushed.com:2001 
@kushedseed.steemed.net:2001 
@steemedseed.steemfeeder.com:2001 
@au1nethyb1steem-id.altexplorer.xyz:2001 
@steem-id46.252.27.1:1337 
@jabbasteemseed.cubeconnex.com:2001 
@bitcube104.40.230.35:2001 
@aizensou45.55.54.83:2001 
@tdv.witness178.63.82.69:2001 
@theprophet0seed.bitcoiner.me:2001 
@bitcoiner89.36.26.82:2001 
@dragosroua78.46.95.157:2001 
@pcste45.76.13.167:2001 
@chitty85.10.227.254:2001 
@christoff522145.76.140.222:2001 
@chillbillseed.teamsteem.me:2001 
@teamsteemsteem-seed.crypto.fans:2001 
@sc-steemit / crypto.fans85.10.196.211:2001 
@puncakbukitsteemseed.dele-puppy.com:2001 
@puppiessteem.clawmap.com:2001 
@steemptyseed.zapto.org:2001 
@geoffreysteem.imcoins.org:2001 
@dr20735.9.200.119:2001 
@cloh76steemd.steemkr.com:2001 
@ludorumseed.bhuz.info:2001 
@bhuzseed.windforce.farm:2001 
@windforceseed-east.steemit.com:2001
seed-central.steemit.com:2001
seed-west.steemit.com:2001
steem-seed1.abit-more.com:2001 
52.74.152.79:2001 
seed.steemd.com:34191 
anyx.co:2001 
seed.xeldal.com:12150
seed.steemnodes.com:2001
seed.liondani.com:2016 
gtg.steem.house:2001
seed.jesta.us:2001 
steemd.pharesim.me:2001 
5.9.18.213:2001 
seed.rossco99.com:2001 
steem-seed.altcap.io:40696 
seed.roelandp.nl:2001 
steem.global:2001 
seed.esteem.ws:2001 
seed.steemviz.com:2001 
steem-seed.lukestokes.info:2001 
seed.steemian.info:2001
seed.followbtcnews.com:2001 
node.mahdiyari.info:2001
seed.jerrybanfield.com:2001 
seed.curiesteem.com:2001 
seed.riversteem.com:2001 
148.251.237.104:2001 
seed1.blockbrothers.io:2001 
seed.timcliff.com:2001
seed.brandonfrye.us:2001
steemseed-fin.privex.io:2001
seed.jamzed.pl:2001
seed.steem.prcolaco.com:2001
seed1.cryptobot.news:2001
seed.thecryptodrive.com:2001
lafonasteem.com:2001 
104.199.118.92:2001 
steem-seed.furion.me:2001 
seed.minnowshares.net:2001 
seed.firepower.ltd:2001
Also, I thought it would be interesting to see where the seed nodes we have are dispersed geographically. Below is a map showing all of the seed nodes across the world.
(Note, a few of the dots have overlap and represent multiple nodes.)
Seed node operators may want to consider setting up nodes in some of the "underserved" locations.
(Tools used: https://mxtoolbox.com/BulkLookup.aspx and https://app.ipapi.co/bulk/)
If you are a seed node operator and you have a seed node that is not in the final list, please drop by the seed-nodes channel in steem.chat and let us know, or reply here with the information about your seed node.