RARLab (the company who make WinRAR) have just released an Android app. Best of all, it's completely free!

Download: Google Play

RARLAB's RAR for Android can create RAR and ZIP and unpack RAR, ZIP, TAR, GZ, BZ2, XZ, 7z, ISO, ARJ archives. List of functions include repair command for damaged ZIP and RAR files, benchmark function compatible with RARLAB's WinRAR benchmark, recovery record, usual and recovery volumes, encryption, solid archives, utilizing multiple CPU cores to compress data.

Additionally to standard ZIP files, unzip function supports ZIP and ZIPX with BZIP2, LZMA and PPMd compression. Unrar command is available for all versions of RAR archives including the latest RAR5. Both UDF and ISO9660 ISO file format can be unpacked.