Convert epoch timestamp to UTC
$ date -u -d @1312398568
Mi 3. Aug 19:09:28 UTC 2011
In vim one can move the cursor over the number and issue :!dump -u -d @<cword> in normal mode.
Format the output of a command and save it to a PDF file
$ ls -la /dev | a2ps --center-title="Sample Report" -r2 -o - | ps2pdf - /tmp/test.pdf
Convert decimal value to hex and use lowercase letters
$ echo "obase=16;7232811" | bc | tr "[:upper:]" "[:lower:]"
Convert hexadecimal value to decimal
$ echo "ibase=16;7FFF | bc