I am more or less a convert from Prototype.js to jQuery. But the thing I found missing the most in jQuery is the functional style Array methods that are provided in Prototype.js. The methods that I normally use are simple, and I have been just recreating them myself in my projects: like collect, select, each, etc. But it's getting a bit tedious to do this for every new project and so I want a very lightweight library that just has these array methods. However, now that ECMAScript 5 is coming close to fruition, it makes a lot sense to use their method names and semantics. I have found that Safari, Firefox, and Flex all provide these methods already, so why not just jump on the bandwagon?
So, I have implemented these methods for environments that do not have them, as best I can to the spec. The methods are forEach, reduce, reduceRight, map, filter, every, some, indexOf, and lastIndexOf.
The code and more info is at github and this project shall be named: ecma5array. Only less than 70 LOC.