Ken Silverman’s Zip utility. Ken says:

My own version of PKZIP. It’s quite a bit slower, and it’s a bit of a memory hog… but for good reason. KZIP creates smaller .ZIP files than PKZIP with maximum compression enabled! No, I didn’t cheat. You see… during compression, PKZIP gives up after it has found so many matches - this is why it is so fast, and also why KZIP can beat it. .ZIP files created with KZIP are compatible with all of the latest .ZIP software - just that if you use KZIP, your file will be a few percent smaller. Decompression is still very fast, making KZIP the perfect tool for shaving off seconds from download times.

Note: Reader Nicolas gives this product a 5-star rating, and recommends you use it with Ken’s other produt, ZIPMIX.

http://www.advsys.net/ken/utils.htm#kzip