I love GNU Make. The simplicity of Makefiles makes it an extremely versatile and powerful tool. Here is some Makefile-fu I learned over the years.
xclip is a nifty little utlity to make working in the terminal just a little more comfortable. It allows you to copy the contents of files or the output of other programs to the clipboard. Here are some use cases: xclip myfile.txt # Copy file to clipboard ls -l | xclip # Copy program output