Jekor's Core Utilities (jcoreutils)
These are additions and enhancements to GNU Core Utilities (coreutils).
xtee ("cross-tee"/"expanded tee") is a program for building complex pipelines. It resembles the tee command, except that instead of copying stdin to stdout, it copies a file to stdout.
Map a command over each line of stdin.
xargs is nice, but it builds commands. I've found no way to shuffle its input into another program's stdin without using echo (which is prone to errors). map is a simpler program with 1 purpose.
Take sections from each line of stdin.
Like cut, but supports indexing fields from the end.