• theming guide - a complete guide on how to create and share your own pluck themes
• module guide - all you need to know about pluck module development
• functions - list of built in functions
• variables - list of built in variables

• get started contributing code - want to contribute, but don't know how? read this guide!
• coding guideline - a must read for everyone who wants to write code for pluck
• translating pluck - help get pluck available in your language
• languages - take a look at the current status of the available languages

Also take a look at Launchpad, where you can file new bugs. All feature specs for upcoming versions and the development status are listed there too.