Alternatives to GZIPInput/OutputStream with better compression ratios? [closed]

Question

I need to store abitrary binary data (essentially files of various common formats, JPEG, PDF, MS-Office and some other odd files). Slow compression is not a problem, but I'm looking for reasonably fast decompression and as good a compression ratio as I can get.

For now my system immediately stores the data uncompressed and a daemon attempts to compress the data later, for now the only option I have implemented is using GZIP. If the file can be compressed it is transparently replaced with a compressed version by the daemon (thats why slow compression does not bother me at all). If there were more options I would be quite happy to let the daemon try all the choices and go with the one that yields the best compression.

To keep the system simple, I don't want to go through great lengths to integrate stuff that does not support use through the Stream API (like 7-Zip LZMA). Are there any compression implementations beside the GZIP one provided by the JRE that might be useful? FOS preferred.