Originally intended to focus on Carbon Events, ACCELA soon grew to encompass just about any part of the toolbox where I got tired of using plain C APIs. The Carbon Event classes remain the most mature (including window, menu, and control wrappers), and the Navigation Services and Core Foundation classes are also quite useful. There are also some PowerPlant classes, such as an attachment which adds Carbon Event handling to a window.
Many of the ACCELA classes are already being used in the shareware product Icon Machine. I started working on them because PowerPlant's Carbon Event support was so slow in coming.
ACCELA is a somewhat contrived acronym, standing for A Cool Carbon Event Library for Applications. You can substitute another C word if you think "cool" sounds silly.
To see what's going on, go to the ACCELA SourceForge project page.