My ~/.bash_profile, with handy command-prompt display of ruby version, gemset, and git branch.

.bash_profile

ESC="\033" # This is the escape sequence
NO_COLOR="$ESC[0m"
IRED="$ESC[1;31m" # ANSI color code for intense/bold red
IGRN="$ESC[1;32m" # ANSI color code for intense/bold green

# From http://railstips.org/blog/archives/2009/02/02/bedazzle-your-bash-prompt-with-git-info/
# I had to change 'git-symbolic-ref' to 'git symbolic-ref'
function parse_git_branch {
  ref=$(git symbolic-ref HEAD 2> /dev/null) || return
  echo " ["${ref#refs/heads/}"]" # I wanted my branch wrapped in [], use () or <> or whatever
}

# from http://ariejan.net/2010/04/25/ruby-version-and-gemset-in-your-bash-prompt-yes-sir
function rvm_version {
  local gemset=$(echo $GEM_HOME | awk -F'@' '{print $2}')
  [ "$gemset" != "" ] && gemset="@$gemset"
  local version=$(echo $MY_RUBY_HOME | awk -F'-' '{print $2}')
  [ "$version" != "" ] && version="$version"
  local full="$version$gemset"
  [ "$full" != "" ] && echo "${full}:" # the colon at the end is a delimiter, you could use a space instead
}

#PS1="\h:\W \u\$" # For reference, here's the default OS X prompt
#export PS1="\$(rvm_version)\W \$(parse_git_branch)\$ " # Without the colors

# I had to put the \[ and \] down here, as opposed to $IRED, to avoid wrapping funkiness.
export PS1="\[$IRED\]\$(rvm_version)\[$NO_COLOR\]\W\[$IGRN\]\$(parse_git_branch)\[$NO_COLOR\] \$ "

[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm" # Load RVM into a shell session *as a function*

alias b='bundle exec'
alias brake='bundle exec rake'