If you want a server that is pure vanilla survival mode minecraft with no plugins, there is no better one that I've been on than Craftdiggers. The owner is Dio_Demonic. It's a great vanilla server, but it's on Hard mode, so you better be prepared. Hackers will be banned.
Two creative mode servers I like are ChasmCraft and PFK-Craft. ChasmCraft utilizes the common plot system, while PFK Craft is more like singleplayer Creative mode in that you can build anywhere in the world (as long as it's not in a protected area). You rank up as you spend time on it and you get new commands the further up you go. You also can only place certain blocks if you are a certain rank. Be warned: there is a big spawn that displays a lot of rules and data on the server. Read it all and then you'll take a 7 question quiz containing stuff that you read. You must answer all 7 questions correctly to begin building. Despite that, it's a great server.