I don't fully understand the use of the letter document class. One reason being exemplified in this "template." It is just as easy to use the default article document class to obtain a similar (and much more flexible) result:

\documentclass{article} % Uses 10pt
\usepackage[
margin=1in, % All margins are 1 inch
]{geometry}% http://ctan.org/pkg/geometry
\pagestyle{empty}
\begin{document}
\begin{flushleft}
\large\bfseries Susan R.\ Bumpershoot
\end{flushleft}
\medskip\hrule height 1pt
\begin{flushright}
1985 Storm Lane, Troy, NY 12180 \\
(518) 273-0014 or (518) 272-6666
\end{flushright}
\bigskip
\noindent \today
\bigskip
\noindent
\begin{tabular}{@{}l}
Ms. Terri Roberts \\
Senior Staff Recruiter \\
XYZ Corporation \\
Rt. 56 \\
Anytown, New Jersey 05867
\end{tabular}
\bigskip
\noindent Dear Ms. Roberts:
\setlength{\parskip}{\baselineskip}
\noindent PARAGRAPH ONE: State reason for letter, name the position or type
of work you are applying for and identify source from which you
learned of the opening. (i.e. Career Development Center,
newspaper, employment service, personal contact).
\noindent PARAGRAPH TWO: Indicate why you are interested in the position,
the company, its products, services - above all, stress what you
can do for the employer. If you are a recent graduate, explain
how your academic background makes you a qualified candidate for
the position. If you have practical work experience, point out
specific achievements or unique qualifications. Try not to repeat
the same information the reader will find in the resume. Refer
the reader to the enclosed resume or application which summarizes
your qualifications, training, and experiences. The purpose of
this section is to strengthen your resume by providing details
which bring your experiences to life.
\noindent PARAGRAPH THREE: Request a personal interview and indicate your
flexibility as to the time and place. Repeat your phone number in
the letter and offer assistance to help in a speedy response. For
example, state that you will be in the city where the company is
located on a certain date and would like to set up an interview.
Or, state that you will call on a certain date to set up an
interview. End the letter by thanking the employer for taking
time to consider your credentials.
\noindent Sincerely yours,
\bigskip \bigskip
\noindent Susan R.\ Bumpershoot % name for signature
\noindent encl: % Enclosures
\end{document}
The use of \noindent is a bit much, but I'm not sure whether you might need indented paragraphs in your letter. If not, you could just set \setlength{\parindent}{0pt} in the document preamble.
geometry provides the layout specification. margin=1in will set a 1in margin (top, bottom, left and right) for all pages.
Also see Adding a signature on an online job application for adding a signature to your letter.
\vfillline would achieve the desired results. – Peter Grill Dec 19 '12 at 5:58