http://godcraft.com/ (Read Below First)
This lovely set of servers is hosted by our lovely Kane_Hart (he also funds this very website for free, FOR the community)
Now, when you first check out the site you'll soon learn that this isn't a free server, and you'll learn why really quickly. Sure it costs $10 or so to join, but what you get for that $10 is by far the most amazing server I've ever seen.
#1 - I'm personally on the new Industrial Server (IC/BC/RP/CC (No Turtles, but Wifi is 9000 blocks long)), I've never seen less than 5 people online and normally it's closer to 10.
#2 - I have HORRIBLE internet and this is easily "playable" for me. Anyone with real internet would notice VERY MINIMUM LAG.
#3 - The whole point of paying $10 or so is to prevent griefers and people that arn't serious about joining an amazing community, this means that the servers are not only full of an amazing set of guys/gals, but you don't have to worry about your stuff being destroyed when you log off for the night.
You can find more about the server and the community on the website above, I give this server and the community 9.5/10!
If you have any questions, feel free to ask Kane_Hart in irc, or on the godcraft forums, you could also find me in irc or here as well I guess but I can't help you with anything more than just my experiences with the server :unsure:/>/>