If you're looking for a simple, easy-to-use, archiving program that supports all the major formats (Zip, 7Zip, Rar, etc.) plus some you'll likely never need, then Peazip is definitely a program you should be looking at. The interface is clean and the program works well, however, it's a bit on the slow side.
Peazip has improved its performance a bit since the last time I gave it a whirl. Previously it lagged badly, this time not as badly, but my standby WinRAR remains much faster. PeaZip also underreported its progress on a multipart 1.5GB RAR file that I tested it with. If it had indeed taken the two minutes the progress bar indicated it might take, I would've ditched it again. It took only 45 seconds.
Other formats supported by PeaZip 4.2 are: ACE, ARC/WRC, ARJ, BZ2, CAB, CPIO, GZ, ISO, IDF, LHA, LZH PAQ, QUAD/BALZ, TAR, ZIPX, Z, various Linux packages, and Mac DMG and HFS. That's hefty list indeed, and if you'd heard of all of them, you're one up on me.
I do have two other minor nits with Peazip. The first is that when you right-click, Peazip operations are only available on a sub-menu. Archiving is one of my major right-click tasks and I'd prefer the ability to place Peazip options directly on the root menu. Also, the only way to browse the network seems to be with Open/Open Path--the network isn't directly available in a browser window.
Installing Peazip is easy, but it is the first program I've seen that asked to install Internet Explorer 9--at least the first time. When I installed it on a second PC, it wanted to install the AOL toolbar. To avoid installing anything extra, choose the custom installation and deselect whatever it offers you. To set context menu entries and file associations, you run the same wizard that's used during the install process. It's found under System Integration in the tools menu.
Peazip has a nice interface and I love the wide file support. For a freebie, it's great, though it would be greater if it were faster.
Note: In addition to the 32-bit and 64-bit editions, PeaZip is also available in a portable edition that requires no installation and can be run from a flash drive. Both editions are free, but the authors accept donations.