filled \diamondsuit and \heartsuit

As Alan has pointed out, the symbols are available in arev, which does normally change all your fonts. The following (added to your preamble) only takes the two symbols you want from arev.

\DeclareSymbolFont{extraup}{U}{zavm}{m}{n}
\DeclareMathSymbol{\varheart}{\mathalpha}{extraup}{86}
\DeclareMathSymbol{\vardiamond}{\mathalpha}{extraup}{87}

Unfortunately the style differs slightly from the default symbols:

$\heartsuit\varheart\diamondsuit\vardiamond\clubsuit\spadesuit$

The arev package provides \varheart and \vardiamond which are filled. (The Comprehensive LaTeX Symbols Guide is your friend here.)

\documentclass[12pt]{article}
\usepackage{arev}
\begin{document}
$\heartsuit\varheart\diamondsuit\vardiamond\clubsuit\spadesuit$
\end{document}

Since arev changes the math font, it's maybe not the best solution. (But see Caramdir's answer for a way around that.)

The txfonts packages also provides \varheartsuit and \vardiamondsuit, but again changes the math font.

\documentclass[12pt]{article}
\usepackage{newtxtext,newtxmath}
\begin{document}
$\heartsuit\varheartsuit\diamondsuit\vardiamondsuit\clubsuit\spadesuit$
\end{document}

Alternatively, if you use XeLaTeX or LuaLaTeX, there are many fonts that contain these characters.

\documentclass{article}
\usepackage{fontspec}
\newfontfamily\suitfont{Dejavu Sans}

\begin{document}
{\suitfont♠︎♣︎♥︎♦︎♤♧♡♢}
\end{document}

\usepackage{fdsymbol}

\clubsuit
\vardiamondsuit
\spadesuit
\varheartsuit