One of my best interest is file archiving.
I actually spent lots of time thinking and implementing compression algorithm.
Today I encountered a good web page:
Maximum Compression : http://www.maximumcompression.com
It showed me which one is good compression software.
And it stroke me there are two good compression software which I haven't heard at all.
I know "winzip," "gzip," and "bzip2."
But the web page showed me PAQ8 is best in the sense of size.
"What is PAQ8???"
It was newly developed archiving software. And it has GPL license, which is totally free.
It does not seem anybody can use yet. It is still changing fast.
One of interesting point is we can choose how much memory we will use for archiving, from 35MB to 1.7G.
The more memory you use, the smaller file you can get.
I love to see its algorithm when I can afford.