Completely EDIT 2012-03-04:
I uploaded the new version 1.3 to CTAN. At the moment the files are available at github.
This version provides a key named shadow. This allows to draw a shadow. The shadow can be manipulated by the new keys shadowsize and shadowcolor
If you use framemethod=tikz it is important to load the TikZ library shadows.
mdframed can do the job but I don't want to load any libraries.
For the methods TikZ and PSTricks I defined a style mdfshadow by tikzset / newpsstyle. For more settings manipulate this key.
Based of the new modification I created the following example:
\documentclass{article}
\usepackage[framemethod=tikz]{mdframed}
\usepackage{lipsum}
\usetikzlibrary{shadows}
\newmdenv[tikzsetting={fill=green!20},
roundcorner=10pt,shadow=true]{myshadowbox}
\begin{document}
\begin{myshadowbox}
\lipsum[2]
\end{myshadowbox}
\lipsum[3]
\begin{myshadowbox}
\lipsum
\end{myshadowbox}
\end{document}
The result is:
An other example is provided in file mdframed-example-pstricks.pdf which uses pstricks and frametitle:
\documentclass{article}
\usepackage{xcolor}
\usepackage[framemethod=pstricks]{mdframed}
\usepackage{lipsum}
\newmdenv[%
shadow=true,
shadowsize=11pt,
linewidth=8pt,
frametitlerule=true,
roundcorner=10pt,
]{myshadowbox}
\begin{document}
\begin{myshadowbox}[frametitle={Der Beweis}]
\lipsum[2]
\end{myshadowbox}
\end{document}
One option using singleextra, firstextra to place the title, instead of frametitle; in this way you can easily obtain the desired shading effect for the background. To control the shadow attributes, you can use all the available keys for example scale, xshift, yshift (refer to the PGF manual). For frames without page breaks a decoration was added midways vertically on the right side (as requested in a comment):
\documentclass{article}
\usepackage[a6paper]{geometry}% just for the example
\usepackage[framemethod=tikz]{mdframed}
\usepackage{amsmath,amssymb}
\usetikzlibrary{calc}
\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes.symbols}
\usetikzlibrary{shadows}
\newcounter{exe}
\newenvironment{Fancybox}[1][\textwidth]
{\stepcounter{exe}%
\mdfsetup{
singleextra={%
\node[draw=blue!40,anchor=east,rectangle, thick,font=\color{black}, double,
top color=blue!40,
bottom color=blue!5,
rounded corners=8pt,
drop shadow={shadow xshift=1.5pt, shadow yshift=-1.5pt},anchor=west
] at ([xshift=20pt]O|-P)
{\strut Example~\theexe};
\path let \p1=(P), \p2=(O) in node[fill=blue!40,font=\color{white}] at (P|-0,0.5*\y2+0.5*\y1) {$\clubsuit$};},%
firstextra={%
\node[draw=blue!40,anchor=east,rectangle, thick,font=\color{black}, double,
top color=blue!40,
bottom color=blue!5,
rounded corners=8pt,
drop shadow={shadow xshift=1.5pt, shadow yshift=-1.5pt},anchor=west
] at ([xshift=20pt]O|-P)
{\strut Example~\theexe};},%
skipabove=\topskip,
skipbelow=\topskip,
innertopmargin=18pt,
linecolor=red,%
innerlinewidth=0.8pt,
topline=true,
apptotikzsetting={\tikzset{mdfbackground/.append style={%
shade,top color=blue!35, bottom color=white}}},
frametitleaboveskip=\dimexpr-\ht\strutbox\relax,
roundcorner=5pt,
linecolor=blue,%
innerlinewidth=1pt,
topline=true,
shadow=true,
rightline=true,innerleftmargin=10,innerrightmargin=10,
shadowcolor=blue!40,
}
\begin{mdframed}[userdefinedwidth=#1]\relax%
}
{\end{mdframed}}
\begin{document}
\begin{Fancybox}
To calculate the horizontal position the kinematic differential
equations are needed:
\begin{align}
\dot{n} &= u\cos\psi -v\sin\psi \\
\dot{e} &= u\sin\psi + v\cos\psi
\end{align}
For small angles the following approximation can be used:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
\end{Fancybox}
\begin{Fancybox}
To calculate the horizontal position the kinematic differential
equations are needed:
\begin{align}
\dot{n} &= u\cos\psi -v\sin\psi \\
\dot{e} &= u\sin\psi + v\cos\psi
\end{align}
For small angles the following approximation can be used:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
For small angles the following approximation can be used:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
\end{Fancybox}
\begin{Fancybox}[7cm]
To calculate the horizontal position the kinematic differential equations are needed:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
\end{Fancybox}
\end{document}
Best Answer
By default,
TiKZshadows useopacity=.5andmdframeduses default settings. The problem is thatmdframeddoesn't offer any option to change anything from shadows except their color, so we must go toTiKZto changeopacity, something like\tikzset{every shadow/.style={opacity=1}}seems to work, but it will change opacity for allmdframedboxes.An alternative solution could be to change from
mdframedtotcolorboxwhich offers easily customizable shadows: