This year's API wishlist surveys are now ready for several Autodesk products, as Kean just pointed out, and will remain open until June 3rd, 2011. Here are direct links to the Revit and Navisworks surveys:
The API wishlist survey has a strong influence on the direction of the future API. so please take the time to fill it out.
To quote Kean, it really is worth providing us with your input: it's one of the most direct ways to influence the direction of the Autodesk products you customize or for which you develop applications. Tell us which APIs are most important to you: your feedback will not fall on deaf ears. And if you (optionally) provide your email address in the survey, Kean will send you a copy of the results once they've been compiled.
Thank you in advance for your participation!
I just came across the Revit APP BBS Revit API development FAQ (frequently asked questions) which includes some really useful and succinct information, such as a very clear explanation of the master and slave symbol geometry used for displaying family instances. Other topics cover shared parameters, regeneration, vertex order, from and to room properties, structural elements end releases and beam orientation.