Onehashcreator checksum calculator is small and simple to use, free online and desktop calculator of most popular checkums.
Both desktop and online versions of application can calculate MD5, SHA-1, SHA2-256 and SHA2-512 checksums.
Online version can calculate only checksum of entered text, and desktop version have options to calculate checksums of single file, or all files in selected folder.
Desktop version of OneHashCreator checksum calculator is avaliable as portable app on windows and linux, both 32 and 64bit versions