Ryan Campbell shows how to get the Prototype library up and running, and introduces and documents Protoype's $() function. Form helper functions, getElementsByClassName functions, Element helper functions, Ajax support, timer functions are all covered.
Ryan Campbell volume tests Prototype's each() Enumeration function and finds that although the code is more elegant than the for loops, the overhead is quite heavy, and the performance impact too high. The summary: If basic JavaScript will do the task, then use basic JavaScript