The Ultimate Compression
I have seen the best compression ratio I have ever seen. Last night I compressed a 16 Gig database down to 2. I used the 7-Zip program. Its interface isn't too pleasing to the eye, but you can tell they focus on what's important, the algorithms. It's a GNU project. It allows you to specify the "Dictionary Size" and "Word Size" for the patterns it finds. The more ram you have, the higher the Dict Size you can use. None of the others program support using more than 4 megs for the compression. I chose for 7zip to use about a gig which resulted in a way higher compression. I highly recommend this program for compression of larger databases.
Program | Method | Percent Of original Size
Zip | (Maximum)| 53% (zip didn't support it this big, I had to split it)
Rar | (Best) | 26%
7zip | (Ultra) | 12%