This code doesn't work with versions of moderncv after 2012. Please use ℝaphink's moderntimeline package instead
Here's a way of getting this to work with moderncv. I've defined a new macro, \funkycventry that takes the start and end year and then all the same arguments as cventry, and uses this to draw the timeline bar in the same colour and width as the section headers. If the end year is 0, the bar fades out, and no end year is printed.

\documentclass[]{moderncv}
\usepackage{tikz}
\moderncvtheme[blue]{casual}
\usepackage[scale=0.8]{geometry}
\firstname{John}
\familyname{Doe}
\begin{document}
\maketitle
\tikzset{
startyear/.style={
font=\scriptsize,
name=startyear,
above=3pt,
inner xsep=0pt,
anchor=base west,
},
endyear/.style={
font=\scriptsize,
name=endyear,
below,
inner xsep=0pt,
anchor=north east,
}
}
\def\firstyear{2000}
\def\lastyear{2011}
\pgfmathsetmacro\yearrange{\lastyear-\firstyear}
\newcommand{\funkycventry}[7]{%
\pgfmathsetmacro\endyear{ifthenelse(#2==0,\lastyear,#2)}
\pgfmathsetmacro\startfraction{(#1-\firstyear)/(\lastyear-\firstyear)}%
\pgfmathsetmacro\endfraction{(\endyear-\firstyear)/(\lastyear-\firstyear)}%
\pgfmathsetmacro\ongoing{!(#2==0)}
\cventry{\tikz[baseline=(endyear.north)]{
\fill [sectionrectanglecolor] (0,0)
++(\startfraction*\hintscolumnwidth,0pt)
node [startyear] {#1}
rectangle (\endfraction*\hintscolumnwidth,0.5ex)
node [endyear] {\pgfmathparse{ifthenelse(#2==0,,#2)}\pgfmathresult}
(\hintscolumnwidth,0pt) ;
\ifnum #2=0
\shade [left color=sectionrectanglecolor]
(\endfraction*\hintscolumnwidth-1em,0pt) rectangle ++(1em,0.5ex);
\fi}
}
{#3}{#4}{#5}{#6}{#7}
}
\section{Experience}
\subsection{Vocational}
\funkycventry{2002}{2007}{Job title}{Employer}{City}{}{General description no longer than 1--2 lines.\newline{}%
Detailed achievements:%
\begin{itemize}%
\item Achievement 1;
\item Achievement 2, with sub-achievements:
\item Achievement 3.
\end{itemize}}
\funkycventry{2000}{2011}{Job title}{Employer}{City}{}{Description line 1\newline{}Description line 2}
\subsection{Miscellaneous}
\funkycventry{2005}{0}{Job title}{Employer}{City}{}{Description}
\end{document}