There's also the pv(1) utility on Linux and OS X Homebrew:

  DESCRIPTION
  
       pv  shows the progress of data through a pipeline by giving infor-
       mation such as time elapsed, percentage completed  (with  progress
       bar), current throughput rate, total data transferred, and ETA.

       To use it, insert it in a pipeline between two processes, with the
       appropriate options.  Its standard input will be passed through to
       its  standard output and progress will be shown on standard error.

(edit: formatting)