You could use TikZ for drawing the lunar phases. Here's a command \moon{<day>} that takes the day of the lunar month as an argument and draws the corresponding lunar phase. The symbols scale with the surrounding text, normal TikZ options can be passed using the optional argument, and the standard lunar phase names have been defined as additional macros (\waxingcrescent, \fullmoon, etc.). The code uses the method for drawing 3D circles that Andrew Stacey describes in Drawing simple 3D cylinders in TikZ ^[1].

Edit: I've edited the code to draw the moon more accurately (using a sinusoidal function instead of a linear one). You can now also provide a date to the moon macro for which the moon phase will be drawn. Furthermore, the colour of the moon and the sky can be set using the moon colour and sky colour keys. The key southern hemisphere will flip the diagram vertically.

\foreach \d in {0,2,...,30}{%
    \d: \moon{\d} \\
}

\moon[scale=10]{2011-11-20}

\moon[scale=10,sky colour=blue!50!black,moon colour=yellow,southern hemisphere]{2011-11-20}

\documentclass[border=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calendar,fpu}

\tikzset{
    moon colour/.style={
        moon fill/.style={
            fill=#1
        }
    },
    sky colour/.style={
        sky draw/.style={
            draw=#1
        },
        sky fill/.style={
            fill=#1
        }
    },
    southern hemisphere/.style={
        rotate=180
    }
}

\makeatletter
\pgfcalendardatetojulian{2010-01-15}{\c@pgf@counta} % 2010-01-15 07:11 UTC -- http://aa.usno.navy.mil/cgi-bin/aa_moonphases.pl?year=2010&ZZZ=END
\def\synodicmonth{29.530588853}
\newcommand{\moon}[2][]{%
    \edef\checkfordate{\noexpand\in@{-}{#2}}%
    \checkfordate%
    \ifin@%
        \pgfcalendardatetojulian{#2}{\c@pgf@countb}%
        \pgfkeys{/pgf/fpu=true,/pgf/fpu/output format=fixed}%
        \pgfmathsetmacro\dayssincenewmoon{\the\c@pgf@countb-\the\c@pgf@counta-(7/24+11/(24*60))}%
        \pgfmathsetmacro\lunarage{mod(\dayssincenewmoon,\synodicmonth)}
        \pgfkeys{/pgf/fpu=false}%%
    \else%
        \def\lunarage{#2}%
    \fi%
    \pgfmathsetmacro\leftside{ifthenelse(\lunarage<=\synodicmonth/2,cos(360*(\lunarage/\synodicmonth)),1)}%
    \pgfmathsetmacro\rightside{ifthenelse(\lunarage<=\synodicmonth/2,-1,-cos(360*(\lunarage/\synodicmonth))}%
    \tikz [moon colour=white,sky colour=black,#1]{
        \draw [moon fill, sky draw] (0,0) circle [radius=1ex];
        \draw [sky draw, sky fill] (0,1ex)
            arc (90:-90:\rightside ex and 1ex)
            arc (-90:90:\leftside ex and 1ex)
            -- cycle;
    }%
}
\newcommand{\newmoon}{\moon{0}}
\newcommand{\waxingcrescent}{\moon{\synodicmonth/8}}
\newcommand{\firstquartermoon}{\moon{2*\synodicmonth/8}}
\newcommand{\waxinggibbous}{\moon{3*\synodicmonth/8}}
\newcommand{\fullmoon}{\moon{4*\synodicmonth/8}}
\newcommand{\waninggibbous}{\moon{5*\synodicmonth/8}}
\newcommand{\thirdquartermoon}{\moon{6*\synodicmonth/8}}
\newcommand{\waningcrescent}{\moon{7*\synodicmonth/8}}
\begin{document}\noindent\raggedleft%
\foreach \d in {0,2,...,30}{%
    \d: \moon{\d} \\
}

\ 

\moon[scale=10]{2011-11-20}

\moon[scale=10,sky colour=blue!50!black,moon colour=yellow,southern hemisphere]{2011-11-20}
\end{document}

You can find scores of symbols in the Comprehensive LaTeX Symbol List ^[1]

For the moon phases you'll find that \usepackage{wasysym} will provide

\fullmoon \leftmoon \newmoon \rightmoon

The following provides a possible solution using pstricks. Obviously the code is not as powerful as the tikz solution above, but it will get you started. The presentation of this solution is analogous to the one above:

\foreach \d in {0,2,...,30}{%
\d: \moon{\d} \\    }

\newmoon
\waxingcrescent
\firstquartermoon
\waxinggibbous
\fullmoon
\waninggibbous
\thirdquartermoon
\waningcrescent

\documentclass[border=5mm]{standalone}

\usepackage{pstricks}
\usepackage{pst-plot}

\newcommand{\moon}[1]{%
\begingroup%
\psset{unit=1ex}%
\psset{linewidth=0.02em}%
\def\synodicmonth{29.530588853}%
\def\lunarage{#1}%
\edef\waxswitch{\ifdim\lunarage pt>.5\dimexpr\synodicmonth pt 1\else -1\fi}%
\begin{pspicture}[showgrid=false](-1.1,-.65)(1.1,1)%
    \parametricplot[plotpoints=91]{0}{360}{t sin t cos}%
    \pscustom[fillstyle=solid,fillcolor=black]{%
    \parametricplot[plotpoints=91]{\waxswitch\space 180 mul}{0}{t sin t cos}%
    \parametricplot[plotpoints=91]{0}{180}{t sin \lunarage\space \synodicmonth\space div 1 \waxswitch\space add 4 div add 360 mul cos mul t cos}%
    }%end pscustom
\end{pspicture}%
\endgroup%
}%end moon command

\newcommand{\newmoon}{\moon{0}}% following incremented by one 8th of \synodicmonth:
\newcommand{\waxingcrescent}{\moon{3.69}}
\newcommand{\firstquartermoon}{\moon{7.38}}
\newcommand{\waxinggibbous}{\moon{11.07}}
\newcommand{\fullmoon}{\moon{14.77}}
\newcommand{\waninggibbous}{\moon{18.46}}
\newcommand{\thirdquartermoon}{\moon{22.15}}
\newcommand{\waningcrescent}{\moon{25.84}}

\begin{document}
\begin{minipage}{3cm}
\raggedleft
\foreach \d in {0,2,...,30}{%
    \d: \moon{\d} \\    }

\newmoon
\waxingcrescent
\firstquartermoon
\waxinggibbous
\fullmoon
\waninggibbous
\thirdquartermoon
\waningcrescent

\end{minipage}
\end{document}

Here, I create the moon phases using stacks of simple circles and half circles that have been suitably stretched. In my original answer I started with the syntax

\moon{<B/W color at moon center>}{<direction that color proceeds>}{<"fullness">}

This may seem confusing at first, but really isn't. For example, \moon{W}{r}{.2} means that the moon center is white and the right side of the moon is also the same color (white). The fullness is 0.2; a value of 1 gives a full or new moon, and a value of 0 gives a half moon. The value of "fullness" I take as the cosine of the phase.

However, I upgraded the solution by way of EDIT to provide

\Moon{<day>}

to make it easy on the user, which just converts the <day> into the appropriate parameters for \moon.

\documentclass[11pt]{article}
\usepackage{bbding,stackengine,scalerel,xcolor}
\stackMath
\def\BCF{\mkern-1mu\bigcirc\mkern-1mu}
\def\BCW{\scalerel*{$\textcolor{white}{\CircleSolid}$}{\bigcirc}}
\def\BCB{\scalerel*{$\CircleSolid$}{\bigcirc}}
\def\HClB{\scalerel*{$\HalfCircleLeft$}{\bigcirc}}
\def\HCrB{\scalerel*{$\HalfCircleRight$}{\bigcirc}}
\def\HClW{\scalerel*{$\textcolor{white}{\HalfCircleLeft}$}{\bigcirc}}
\def\HCrW{\scalerel*{$\textcolor{white}{\HalfCircleRight}$}{\bigcirc}}
\newcommand\BC[1]{\csname BC#1\endcsname}
\newcommand\HC[2]{\csname HC#1#2\endcsname}
\newcommand\moon[3]{%
  \if W#1\def\tmp{B}\else\def\tmp{W}\fi%
  \stackengine{0pt}{%
    \stackengine{0pt}{%
      \stackengine{0pt}{\BC{\tmp}}{\scalebox{#3}[1]{\BC{#1}}}{O}{c}{F}{F}{L}%
    }{\HC{#2}{#1}}{O}{#2}{F}{F}{L}%
  }{\BCF}{O}{c}{F}{F}{L}
}
\usepackage{fp}
\newcommand\Moon[1]{%
  \FPeval{\thecos}{cos(2*(#1)*pi/29.5)}%
  \ifnum#1<8\relax\def\mcol{B}\def\colyaw{l}\else%
  \ifnum#1<15\relax\def\mcol{W}\def\colyaw{r}\else%
  \ifnum#1<23\relax\def\mcol{W}\def\colyaw{l}\else%
  \ifnum#1<30\relax\def\mcol{B}\def\colyaw{r}\else%  
  \fi\fi\fi\fi%
  \moon{\mcol}{\colyaw}{\thecos}%
}
\begin{document}
\parbox{1in}{%
\texttt{\textbackslash moon\{\}\{\}\{\}}\par
\moon{B}{l}{1.}\par 
\moon{B}{l}{.7}\par
\moon{B}{l}{.5}\par
\moon{B}{l}{.2}\par
\moon{B}{l}{.0}\par
\moon{W}{r}{.2}\par
\moon{W}{r}{.5}\par
\moon{W}{r}{.7}\par
\moon{W}{r}{1.}\par
\moon{W}{l}{.7}\par
\moon{W}{l}{.5}\par
\moon{W}{l}{.2}\par
\moon{W}{l}{.0}\par
\moon{B}{r}{.2}\par
\moon{B}{r}{.5}\par
\moon{B}{r}{.7}\par
}
\parbox{1in}{%
\texttt{\textbackslash Moon\{$<$day$>$\}}\par
0: \Moon{0}\par
2: \Moon{2}\par
4: \Moon{4}\par
6: \Moon{6}\par
8: \Moon{8}\par
10: \Moon{10}\par
12: \Moon{12}\par
14: \Moon{14}\par
16: \Moon{16}\par
18: \Moon{18}\par
20: \Moon{20}\par
22: \Moon{22}\par
24: \Moon{24}\par
26: \Moon{26}\par
28: \Moon{28}\par
30: \Moon{28}\par
}
\end{document}