Maximum Compression is an excellent site. However, it's focus is on literally that, and not on efficiency. There's a huge difference. Search for "Calgary Corpus" -- good compression benchmark test. There is another one that I'm forgetting at the moment too.
If you're looking for the smallest size, check out the PAQ8i or similar PAQ compression tools. However, keep in mind that PAQ compression at maximum is SLOW! The gains generally aren't worth it.
A few good compression algorithms with high efficiency: RAR, PPMd, ACE, BZip2. They vary, but all achieve good efficiency. (They don't beat PAQ for maximum compression though.)
No - not touting ALZ compression as it's geared towards massive archives, and not high compression ratios. It uses DEFLATE/ZIP compression, which while good, aren't the best for high compression ratios.
I don't care how long it takes but I do want it to be absolutely as small as I can get it.
Try PAQ on maximum compression then try to say that again.