Powerlet is described as 'Quickly find and run your bookmarklets' and is an app in the Web Browsers category. There are nine alternatives to Powerlet for a variety of platforms, including Mac, Windows, Linux, Firefox and Online / Web-based. The best alternative is Greasemonkey, which is both free and Open Source. Other great apps like Powerlet are Tampermonkey (Free Personal), Violentmonkey (Free, Open Source), Userscripts (Free, Open Source) and Shortwave (Free).
Greasemonkey is a Firefox extension that allows you to customize the way webpages look and function. Hundreds of scripts are already available for free. And if youre the tinkerer sort, you can also write your own.
Firemonkey is a totally new combined user-Scripts and user-Style manager. While it has similar functions to other user-Script managers like GreaseMonkey/Tampermonkey/Violentmonkey, and user-CSS managers like Stylish/Stylus/xStyle, there are also differences.