Tail

Robert Daeley has posted a very useful overview of the UNIX command tail at the macdevcenter. His post really sums up the idea that UNIX is full of simple commands that do one thing and do it well (sound like anyone's favorite computer company?). However, just because the tail command is simple doesn't mean it can't be powerful. Coupled with the idea of 'piping' output from one command to another you can accomplish many things.

Robert explains it much better than I ever could so check out his post.