PixelBeat has nice compilation of some of the commonly used Linux terminal commands. The commands are also categorized and should help in finding the right command/command usage for the task at had.
Link: http://www.pixelbeat.org/cmdline.html
Also note the comment in the above page:
Examples marked with • are valid/safe to paste without modification into a terminal, soyou may want to keep a terminal window open while reading this so you can cut & paste.
Don’t forget to Bookmark it for future reference !