I have a whole repository also including several dotfiles that I maintain for already several years [1]. Following are some snippets from the dotfiles/.alias and dotfiles/.functions files from that repository that probably are the most interesting and which I am using on a regular basis:

    # easier navigation
    alias ..="cd .."
    alias ...="cd ../.."
    alias ....="cd ../../.."
    alias .....="cd ../../../.."
    alias ~="cd ~"

    # Get current public ip address
    alias ip="dig +short myip.opendns.com @resolver1.opendns.com"

    # Alias for summing a column
    alias mksum="paste -sd+ - | bc"

    # Export pbcopy / pbpaste to linux 
    if [[ "${OSTYPE}" == "linux"* ]]; then
        alias pbcopy="xclip -selection clipboard"
        alias pbpaste="xclip -selection clipboard -o"
    fi

    # create a new directory and enter it
    function mkd() {
        mkdir -p "$@" && cd "$_";
    }

    # plot stuff directly from the command line.
    # Example: seq 100 | sed 's/.*/s(&)/' | bc -l | plot linecolor 2
    # -> Generate 100 numbers, wrap it in s(<num>) and calc sin(<num>)
    function plot() {
        { echo 'plot "-"' "$@"; cat; } | gnuplot -persist;
    }

    # wrapper for easy extraction of compressed files
    function extract () {
      if [ -f $1 ] ; then
          case $1 in
              *.tar.xz)    tar xvJf $1    ;;
              *.tar.bz2)   tar xvjf $1    ;;
              *.tar.gz)    tar xvzf $1    ;;
              *.bz2)       bunzip2 $1     ;;
              *.rar)       unrar e $1     ;;
              *.gz)        gunzip $1      ;;
              *.tar)       tar xvf $1     ;;
              *.tbz2)      tar xvjf $1    ;;
              *.tgz)       tar xvzf $1    ;;
              *.apk)       unzip $1       ;;
              *.epub)      unzip $1       ;;
              *.xpi)       unzip $1       ;;
              *.zip)       unzip $1       ;;
              *.war)       unzip $1       ;;
              *.jar)       unzip $1       ;;
              *.Z)         uncompress $1  ;;
              *.7z)        7z x $1        ;;
              *)           echo "don't know how to extract '$1'..." ;;
          esac
      else
          echo "'$1' is not a valid file!"
      fi
    }

[1] https://github.com/NewProggie/Dev-Utils