The ext2compr project provides a kernel patch Information about them is located at http://e2ompr.memalpha.cx/e2compr/.
There is also a Web site for the e2compr patches. The code is still experimental and consists of patches for the 2.0 and 2.1 kernels. For more information about the project, including the latest patches, and the address of the mailing list, look up the URL at http://debs.fuller.edu/e2compr/.
[Roderich Schupp, Peter Moulder]
zlibc is a program that allows existing applications to read compressed (GNU gzip'ed) files as if they were not compressed. Look at ftp://metalab.unc.edu/pub/Linux/libs/. The author is Alain Knaff.
There is also a compressing block device driver, "DouBle," by Jean-Marc Verbavatz, which can provide on-the-fly disk compression in the kernel. The source-only distribution is located at ftp://metalab.unc.edu/pub/Linux/patches/diskdrives/. This driver compresses inodes and directory information as well as files, so any corruption of the file system is likely to be serious.
There is also a package called tcx (Transparently Compressed Executables), which allows you to keep infrequently used executables compressed and only uncompress them temporarily when in use. It is located at ftp://metalab.unc.edu/pub/Linux/utils/compress/.