Character Planners
PowerHouse
PowerHouse is an HTML/Javascript character builder for players that allows you to plan out the attributes, powers, and advantages your character(s) will take. It is released under the GPL and is similar to and inspired by championBuilder, which is a Java application that performs a similar function (see the next section).
ChampionBuilder
ChampionBuilder is a great Java application, originally written by Moritz Hartmeier and currently maintained by Roxstar, (also released under the GPL) that allows you to plan out the attributes, powers, and advantages your character(s) will take. The code repository is hosted on Google Code.
Public Test Shard (PTS)
The PTS is the testing shard for Champions Online. Once you sign up for it, you can copy any of your characters from the live shard over. This allows you to test content and powers without modifying the real character. Speak with the "Debugger" by the Power House in Millennium City to change levels and get gear.
Jabber (XMPP Instant Messaging)
Champions Online has XMPP (Jabber) support. This allows you to chat with other players from any instant messaging client that supports XMPP. Here are instructions to set it up.
Key Bindings and Macros
The FAQ for Binds/Commands on the Champions Forum is a great overview of how to set key bindings and macros.