As markjoy says, extractnow is pretty good.
I mostly use
7Zip -
http://www.7-zip.org/ - which is free, easy to use and I think pretty good.
The main features of
7-Zip:
* High compression ratio in new 7z format with LZMA compression
* 7-Zip is free software distributed under the GNU LGPL
* Supported formats:
o Packing / unpacking: 7z, ZIP, GZIP, BZIP2 and TAR
o Unpacking only: RAR, CAB, ISO, ARJ, LZH, CHM, Z, CPIO, RPM, DEB and NSIS
* For ZIP and GZIP formats 7-Zip provides compression ratio that is 2-10 % better than ratio provided by PKZip and WinZip
* Self-extracting capability for 7z format
* Integration with Windows Shell
* Powerful File Manager
* Powerful command line version
* Plugin for FAR Manager
* Localizations for 63 languages
