First you need to decide which of the following categories best describe what you are looking for.
I want an easy all-inclusive start:All-In-One
This category is for people new to XMPP that are looking for an option that combines everything in an easy package.
I am interested in a service for my:Collective
This category is for groups and organisations that need multiple accounts and professional hosting.
I would like to open a:Personal account
This category is for individuals looking for a reliable place to open an account.
Why are there so many options to chose from?
The Jabber network is a large and decentralized effort run by many people and organizations. There is no central company calling all the shots and protocol development is organized collectively through the XMPP Standards Foundation. This means that there are a lot of servers to choose from.
You changed or mind or made a mistake when originally selecting a server? Not a big deal! While account portability is still a work in progress for most of the Jabber network, there is a website that mostly automates it for you here. As it currently requires your user-credentials to function, it would be probably good to change the passwords of both accounts after using this tool.
Can't I just get an account with you?
Sorry, but we do not provide Jabber accounts ourselves. You can learn more about the reasons why here.