Different margins for title page

Using the geometry package it is possible to switch your layout mid-document using the \newgeometry{<settings>} macro. We first set up the initial layout of the title page (1in on all four sides) when the package is loaded

\usepackage[showframe,paper=a4paper,margin=1in]{geometry}% http://ctan.org/pkg/geometry

and then change this after the title page using

\newgeometry{top=1in,bottom=1in,right=0.5in,left=1.5in}

Here is the complete MWE:

\documentclass{article}
\usepackage[showframe,paper=a4paper,margin=1in]{geometry}% http://ctan.org/pkg/geometry
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\begin{document}
\begin{titlepage}
\thispagestyle{empty}
\author{Somebody Important}
\title{Something just as important}
\maketitle
\lipsum[1-2]
\end{titlepage}

\newgeometry{top=1in,bottom=1in,right=0.5in,left=1.5in}

\section{First section} \lipsum[1-4]
\section{Second section} \lipsum[5-8]
\section{Third section} \lipsum[9-12]
\section{Last section} \lipsum[13-16]
\end{document}

lipsum provides dummy text, while the showframe option to geometry merely frames the page to highlight the layout of the text block and other areas.

Using \restoregeometry yields the same results:

\documentclass{article}
\usepackage[showframe,paper=a4paper,top=1in,bottom=1in,right=0.5in,left=1.5in]{geometry}% http://ctan.org/pkg/geometry
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\begin{document}

% Declare new goemetry for the title page only.
\newgeometry{margin=1in}
%---------------------------------------------

\begin{titlepage}
\thispagestyle{empty}
\author{Somebody Important}
\title{Something just as important}
\maketitle
\lipsum[1-2]
\end{titlepage}

% Ends the declared geometry for the titlepage
\restoregeometry
%--------------------------

\section{First section} \lipsum[1-4]
\section{Second section} \lipsum[5-8]
\section{Third section} \lipsum[9-12]
\section{Last section} \lipsum[13-16]
\end{document} 

This gives:

I recommend to set up the title page as a separate small tex file and including the resulting pdf in the main document using package pdfpages.

The content of the titlepage is static anyway, needs extra attention and is the one (hopefully) place in the document where semantinc markup is not needed. There is no real need to keep it with the other stuff. It also ensures correct counting of pages, meaning you don't get in trouble with hyperref.

\documentclass{report}
\usepackage{pdfpages}
\usepackage{hyperref}
\begin{document}
\includepdf{titlepage}
%Acknowledgements, Dedication, Wombats, Ducks etc.
\chapter{Introduction}
\end{document}