mp42avi

CONVERT MP4 to AVI:
ffmpeg -i source.mp4 -vcodec mpeg2video -b 5000k -acodec ac3 -ar 48000 -ab 384k -ac 2 -g 12 -top 1 -target ntsc-dvd -aspect 4:3 source.avi

pdfconcat

How to concatenate a large number of PDFS (for example, GroupOn vouchers):
gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=groupon.pdf Groupon-*.pdf

rsync

RSYNC ENTIRE DIRECTORY:
rsync -avz local_dir remote_user@remote_machine:/remote_path
Recursively copies all files from local_dir to directory
/remote_path/local_dir on remote machine.
Note: trailing slash on source directory avoids creation of local_dir on
remote host