Uncompressor is an app to extract compressed files. Uncompressor currently supports RAR, ZIP, TAR and BZIP2 formats. Just browse to your files, make a long tap on any compressed one (will have different icon to easily location) and choose Extract. That's all.
You can unrar, unzip, untar and unbzip2. Password protected ZIP and RAR files are also supported. Multipart RAR files are also supported.
Be patience when extracting big files, let it finish! Even though you don't see activity, it's working. If something fails it will tell you.