Compression formats with good support for random access within archives?

Question

This is similar to a previous question, but the answers there don\'t satisfy my needs and my question is slightly different:

I currently use gzip compression for som

Answer 1

razip supports random access with better performance than gzip/bzip2 which have to be tweaked for this support - reducing compression at the expense of "ok" random access:

http://sourceforge.net/projects/razip/