I used to use WinZip all the time, but now I mainly use the compressor / extractor built into Windows XP. I use WinRar if I need to open .rar files, and I recently discovered PowerISO, when I needed to open a .daa file, which I had never come across before. I also occasionally use AlphaZip, which opens .tar files, but I've yet to find one that does it all.